All 213 Free Online Tools
Every tool on OnlineToolHubs in one place, grouped across 12 categories. Each one runs in your browser — no account, no install, no upload of your data.
Showing 213 of 213 tools
Calculators (27)
- BMI CalculatorWork out your BMI, and the measurement current NICE guidance asks for alongside it: waist-to-height ratio, which sees where the weight sits when BMI cannot.
- Age CalculatorYour exact age in years, months and days plus every other unit, the weekday you were born, your next birthday, and a proper answer for 29 February birthdays.
- Percentage CalculatorA percentage calculator with the working shown: percent of a number, percent change, percent difference, reverse percentage and weighted average.
- Tip CalculatorA tip calculator that works on the pre-tax or post-tax amount and shows what the choice costs, splits any number of ways, or works back from a round total.
- Unit ConverterA unit converter across 12 categories and 90+ units that shows the factor used — and whether it is exact by definition or merely conventional.
- Standard Deviation & Variance CalculatorA standard deviation calculator for sample and population, with the full working, relative standard deviation, and how much n−1 changes the answer.
- Standard Normal Z-Score & Percentile CalculatorA z score calculator both ways — score to percentile and back — with the step most skip: for a sample mean the divisor is σ/√n, not σ.
- Scientific & Engineering Notation ConverterA scientific notation converter for decimal, E-notation and engineering form without losing digits — and a warning when a value exceeds exact range.
- Quadratic Equation Formula SolverA quadratic equation solver for ax² + bx + c = 0: the discriminant step by step, real or complex roots, and the vertex of the parabola.
- Right Triangle Trigonometry & Pythagorean CalculatorA right triangle trig calculator solving from any two values: sides, angles, area, altitude, inradius and circumradius, with the working shown.
- Circle Area, Circumference & Diameter CalculatorSolve a circle from radius, diameter, circumference or area — plus arc length, sector, chord and segment, which the top results describe but never compute.
- Fraction Arithmetic & Simplifier CalculatorAdd, subtract, multiply and divide fractions — including mixed numbers and a third fraction, which the top-ranking calculator does not accept.
- Significant Figures Counter & Rounding CalculatorCount significant figures and round correctly — including the ambiguous cases like 100 and 1000, and the round-half-to-even rule most calculators skip.
- Matrix Determinant Calculator (2×2 to 5×5)Determinants for 2×2, 3×3, 4×4 and 5×5 matrices with the cofactor expansion shown — exact for integer inputs, so a singular matrix reads 0 rather than 1e-16.
- Logarithm & Natural Log (ln) CalculatorSolve for any part of log₆(x) = y — the logarithm, the antilog or the base — with the change-of-base working shown, in base 10, 2, e or any other.
- Prime Number Tester & Factorization GeneratorPrime factors, divisor count and primality — plus the square root in simplest radical form, which no other calculator derives from the factorization.
- Permutations (nPr) & Combinations (nCr) CalculatornPr and nCr with and without repetition — all four cases, in exact arbitrary precision, where most calculators cover two and break on large numbers.
- Recipe Portion & Serving Size ScalerScale recipe ingredient quantities up or down automatically by serving size or party count. Handles fractions, cups, grams, and teaspoons. 100% free.
- Baking Yeast Ratio Converter (Instant, Active & Fresh)Convert between Instant Dry Yeast (IDY), Active Dry Yeast (ADY), and Fresh Compressed Cake Yeast with precision baking weight and volume ratios.
- Specialty Coffee Brew Ratio CalculatorCalculate golden coffee-to-water brewing ratios (1:15 to 1:18) for Pour Over (V60/Chemex), French Press, AeroPress, Cold Brew, and Espresso.
- Meat & Poultry Roasting Temperature TimerCalculate oven roasting times, temperatures, and USDA-recommended internal meat thermometer temperatures for Beef, Turkey, Chicken, Pork, and Lamb.
- Sourdough Hydration & Baker’s Percentage CalculatorCalculate artisan sourdough dough hydration percentages, main flour, water, 100% hydration starter/levain, and salt weights with baker’s math.
- Boiled Egg Cooking Timer (Soft, Jammy & Hard)Exact boiling times for soft, jammy and hard-boiled eggs. Adjusts for egg size, fridge-cold or room-temperature start, and your altitude.
- Airline Luggage Weight (KG to LBS) & Dimension ConverterConvert luggage weights between kilograms (kg) and pounds (lbs). Checks standard airline baggage allowances (23kg / 50lbs / 32kg) and cubic volume.
- Camera Sensor Crop Factor & Focal Length EquivalentCalculate 35mm full-frame equivalent focal length (mm), field of view classification, and equivalent depth of field aperture across APS-C and Micro 4/3 sensors.
- Photography Exposure Value (EV) & Lux CalculatorCalculate photography Exposure Value (EV100), ambient scene illuminance in Lux, and aperture/shutter/ISO exposure triangle reciprocity settings.
- Golden Hour & Blue Hour Photography Lighting CalculatorCalculate morning and evening Golden Hour and Blue Hour natural light windows from local sunrise and sunset times for portraits and landscape photography.
Currency & Finance (36)
- Mortgage CalculatorA mortgage calculator with full PITI, the exact month PMI ends under federal law, the crossover month, and what extra principal actually saves.
- Currency ConverterA currency converter for 166 currencies at the mid-market rate, plus what a card, bank or bureau actually gives you once the markup is applied.
- Compound Interest CalculatorA compound interest calculator with contributions on their own schedule, the effective annual rate, a today's-money figure and exact doubling time.
- Loan Payoff CalculatorSee how extra payments cut your loan short. Get payoff date, total interest saved, and the full month-by-month amortization schedule. Free, no signup.
- Salary & Tax CalculatorA salary tax calculator using 2026 IRS brackets and the $184,500 Social Security cap. Shows federal, FICA, state and why a bonus looks over-taxed.
- Crypto Profit CalculatorCalculate cryptocurrency investment returns, net profit/loss, and exchange fees with live prices for Bitcoin, Ethereum, Solana, and altcoins. 100% free.
- Auto Loan CalculatorEstimate your car payment with tax and trade-in, then see how long each term leaves you underwater. Compare 36 to 84 months. Free, no signup.
- Retirement & 401(k) CalculatorA retirement calculator that projects your nest egg with the 4% rule — plus what a single-average projection hides: sequence-of-returns risk.
- Credit Card Payoff CalculatorCalculate how long to pay off your credit card balance, total interest costs, minimum payments, and interest saved by paying extra monthly. 100% free.
- Simple Interest CalculatorA simple interest calculator showing the 365- and 360-day conventions side by side — the difference lenders rely on and most calculators ignore.
- Inflation & Purchasing Power CalculatorAn inflation calculator running on the official BLS CPI-U series, the same data the government calculator uses, plus a labeled future projection.
- Net Worth CalculatorA net worth calculator that benchmarks your total against the Federal Reserve median for your age band — not the average, which is 5.5x the middle.
- Certificate of Deposit (CD) CalculatorCalculate certificate of deposit maturity earnings, APY compounding interest (daily, monthly, annually), and total interest payout. 100% free.
- Hourly to Salary ConverterAn hourly to salary calculator with FLSA overtime, paid versus unpaid leave side by side, and what FICA takes before you see any of it.
- Down Payment Savings CalculatorA down payment calculator for the cash you actually need — down payment plus closing costs — whether PMI applies, and what it does to the monthly payment.
- Stock & Crypto Average Down CalculatorA stock average calculator for your average entry price across every buy lot — the price a holding must reach to break even, before fees and tax.
- Future Value (FV) CalculatorA future value calculator for a lump sum plus recurring monthly contributions, showing how much of the result each part actually produced.
- Capital Gains Tax CalculatorA capital gains tax calculator for stocks and for a house sale: 2026 IRS brackets, the $250k/$500k home exclusion, depreciation recapture and the 3.8% NIIT.
- Cryptocurrency Market Cap & Price TrackerTrack real-time cryptocurrency prices, 24-hour trading volumes, price percentage changes, and total market capitalization. Powered by CoinGecko API.
- Ethereum Gas Fee & Gwei TrackerEstimate real-time Ethereum network gas fees in Gwei and USD for ETH transfers, ERC-20 token sends, Uniswap swaps, and NFT minting. 100% free.
- Gold & Silver Bullion Karat Price CalculatorCalculate the spot melt value of gold and silver bullion, coins, and jewelry across 24k, 22k, 18k, 14k, and 10k purities in grams, tola, and troy ounces.
- Bitcoin Halving Countdown & Reward ScheduleTrack the exact countdown to the next Bitcoin Halving event, remaining block height, historical mining rewards, and programmatic inflation reduction schedule.
- Total Compensation (TC) & Salary CalculatorCalculate and negotiate your true total compensation (TC) package including base salary, annual bonus, stock equity (RSUs), 401(k) match, and benefits.
- Rule of 72 Compound Interest CalculatorA Rule of 72 calculator for how long money takes to double at a given rate — and where the shortcut is accurate, and where it drifts.
- Rent vs Buy Real Estate CalculatorFind the year buying beats renting, counting selling costs and the investment return you give up on the down payment. Includes the 5% rule check.
- Crypto Staking APY & Compounding CalculatorCalculate crypto staking rewards, daily compounding returns, and monthly passive income in tokens and USD across variable APY/APR rates. 100% free.
- Fixed Annuity Monthly Payout CalculatorAn annuity payout calculator for fixed-period annuities: monthly and annual income from a lump sum, and how that differs from a life annuity quote.
- Emergency Fund & Safety Net CalculatorAn emergency fund calculator sized from essential expenses — 3, 6, 9 or 12 months by income stability — and how long it takes at your saving rate.
- Auto Lease vs Buy & Cost of Ownership CalculatorA car lease vs buy calculator comparing the true cost of each: monthly payments, money down, interest, and the resale equity a lease never builds.
- Stock Dividend Yield & DRIP CalculatorA dividend yield calculator with annual income, DRIP compounding and yield on cost — plus why a rising yield is often the share price falling.
- Stock Options Profit & Breakeven SimulatorCalculate net profit, loss, breakeven stock prices, and return on capital for Long Call and Long Put stock options contracts at expiration. 100% free.
- Home Equity & HELOC Borrowing CalculatorA home equity loan calculator for borrowing capacity and the exact monthly payment, including HELOC draw-period shock. No signup, no personal details.
- Loan & Mortgage Amortization ScheduleA loan amortization schedule generator producing every payment row, not a summary. Download as CSV for Excel, print it, compare biweekly payments.
- Net Effective Rent & Concession CalculatorA net effective rent calculator for the real monthly cost of a lease once free months, concessions and upfront admin fees are spread across it.
- Commercial Real Estate Cap Rate CalculatorCalculate commercial real estate Capitalization Rate (Cap Rate), Net Operating Income (NOI), and Gross Rent Multiplier (GRM) for investment properties.
- Vacation & Travel Daily Budget PlannerEstimate total vacation and travel trip expenses including hotels, daily dining, local transit, museum activities, flights, and a 10% emergency buffer.
Developer Tools (44)
- JSON Formatter & ValidatorFormat and validate JSON in your browser, nothing uploaded. Covers the six value types, why trailing commas fail, and the 2^53 precision trap on large IDs.
- Base64 Encoder & DecoderA Base64 encoder decoder for text, covering the URL-safe alphabet, padding and the 33% size overhead — and why Base64 is not encryption.
- URL Encoder & DecoderA URL encoder decoder with a full percent-encoding reference and the encodeURI vs encodeURIComponent difference that quietly breaks query strings.
- Regex TesterTest regular expressions live against the JavaScript engine, with a flavor comparison for Python, Java, .NET and PCRE, and catastrophic backtracking warnings.
- Password GeneratorA password generator with a passphrase mode: six random words is 77.5 bits, the same as a 12-character password. Runs in your browser; nothing is uploaded.
- Diff Checker & Text CompareCompare two texts side by side in your browser, nothing uploaded. Explains unified diff format and why CRLF line endings make every line look changed.
- CSV to JSON ConverterConvert CSV to JSON in your browser, with control over type inference so leading zeros survive. Covers the Excel BOM and semicolon-delimiter traps.
- Markdown Live PreviewerWrite and preview GitHub-flavored markdown in real time. Features instant split-screen HTML rendering, code syntax styling, and one-click HTML copy.
- HEX to RGB Color ConverterA HEX to RGB converter that also gives RGBA, HSL and CMYK, with a live picker, contrast check, and the 8-digit hex alpha notation explained.
- HTML to Markdown ConverterConvert HTML code snippets, articles, and rich text to clean GitHub-flavored markdown with code fences, headers, blockquotes, and lists.
- Cryptographic Hash GeneratorGenerate secure cryptographic checksums and hashes (SHA-256, SHA-512, SHA-384, SHA-1) directly in your browser using the Web Crypto API.
- JWT Token Decoder & InspectorA JWT decoder that also verifies the signature in your browser: HS256 with a secret, RS256 and ES256 with a public key. Claims, expiry and alg:none flagged.
- Cron Expression GeneratorA cron generator with plain-English output, common recipes, and the field-count differences for Quartz, Spring and AWS that break copied expressions.
- SQL Formatter & BeautifierFormat SQL for readable diffs and code review, with an identifier-quoting table for PostgreSQL, MySQL, T-SQL, Oracle and Spark SQL. Runs in your browser.
- UUID / GUID v4 GeneratorA UUID generator for bulk, cryptographically secure Version 4 UUIDs and GUIDs, with uppercase and hyphen-removal options. Runs in your browser.
- Unix Epoch Timestamp ConverterConvert Unix epoch timestamps (seconds & milliseconds) to human-readable UTC and local dates, or convert any date to Unix epoch timestamps. 100% free.
- HTML Entity Encoder / DecoderEncode and decode HTML entities with a full reference table, plus why entity encoding alone is not safe inside script blocks, URLs or CSS.
- cURL Command to Code ConverterA curl converter that turns a pasted command into Fetch, Axios and Python requests code, parsed in your browser with nothing sent anywhere.
- CSS Box Shadow GeneratorA CSS shadow generator with sliders for offset, blur, spread and color, plus layering, inset, live preview and one-click copy of the box-shadow.
- CSS Gradient GeneratorCreate vibrant CSS linear and radial gradients with custom color stops, angles, designer presets, and 1-click CSS code export. 100% free.
- SEO URL Slug GeneratorTurn any title into a clean lowercase URL slug. Covers accent stripping limits, why hyphens beat underscores, and the redirect you need if a slug changes.
- DNS Record & Nameserver InspectorInspect live DNS records, mail exchangers (MX), SPF/TXT records, and nameservers for any domain using Cloudflare DNS-over-HTTPS. 100% free.
- HTTP Status Code ExplainerHTTP status code lookup for every standard response code — 200, 301, 404, 500, 502, 503 — in plain English, with what to do about each one.
- User Agent & Browser InspectorA user agent analyzer for your own browser string: operating system, browser engine, version, screen resolution and device pixel ratio, parsed locally.
- IP Subnet Mask & CIDR CalculatorA subnet mask calculator for IPv4: CIDR prefix, network and broadcast address, usable host range, wildcard mask and host count from any address.
- SSL / TLS Certificate & Security InspectorAn SSL certificate checker with an honest limit: a browser can prove the handshake succeeded, not read the certificate. What that does and does not prove.
- TCP / UDP Port Database ReferenceSearch common TCP/UDP network ports (22, 80, 443, 3306, 5432, 8080) with protocol definitions, standard service names, and security recommendations.
- JSON to XML & XML to JSON ConverterA JSON to XML converter that runs both directions and re-parses its own output before showing it, so what you copy is known to be well-formed.
- JSON to YAML & YAML to JSON ConverterA JSON to YAML converter that runs both ways in your browser, covering implicit typing: why 1.20 becomes 1.2 and unquoted NO can become false.
- MAC Address & OUI Vendor LookupMAC address lookup against the IEEE OUI registry: identify the manufacturer — Apple, Cisco, Intel, Samsung — behind any address or vendor prefix.
- HTML, CSS & JSON Code Minifier & FormatterMinify and beautify HTML, CSS, and JSON code client-side. Reduce file payload size, strip whitespace, and improve website loading speed.
- Interactive Regex Builder & TesterTest and debug regular expressions in real-time with group capture inspection, flag switches (g, i, m), and ready-to-use cheatsheet presets.
- JSON API Mock Test Data GeneratorGenerate realistic mock JSON data arrays for frontend testing and prototyping. Includes User Profiles, Ecommerce Products, and Order schemas.
- Linux Chmod Permissions CalculatorCalculate Linux/Unix file permissions with interactive read, write, and execute checkboxes. Generates octal (755, 644) and symbolic permissions.
- Markdown Table Generator & SpreadsheetCreate and format Markdown tables using a visual spreadsheet editor. Add rows, columns, adjust text alignment (left, center, right), and copy clean markdown.
- WCAG 2.2 Color Contrast Ratio CalculatorA color contrast checker for text and background: the WCAG 2.2 ratio with AA and AAA pass/fail for normal and large text, plus a live preview.
- RFC 4648 Base32 Encoder & DecoderEncode text to Base32 or decode Base32 strings into plain text using standard RFC 4648 alphabet. Essential for two-factor authentication (2FA) OTP keys.
- JWT (JSON Web Token) Builder & SimulatorA JWT builder that signs for real with Web Crypto HMAC-SHA256, plus decode and verify. Runs in your browser — but never paste a live secret.
- Security HTTP Response Header GeneratorGenerate HSTS, Content-Security-Policy, X-Frame-Options, Referrer-Policy and Permissions-Policy response headers, with preload gated behind a warning.
- Social Open Graph & Twitter Card GeneratorAn Open Graph generator for og: and Twitter Card meta tags, with a live preview of how the link renders on Facebook, LinkedIn, X and Discord.
- SEO Robots.txt & Sitemap Directives GeneratorA robots.txt generator with correct Allow/Disallow precedence — and why Disallow blocks crawling but does not stop a URL from being indexed.
- Binary, Decimal & Hex ConverterA binary decimal hex converter (and octal) with arbitrary precision, so 64-bit values stay exact. Invalid digits are rejected, not silently dropped.
- Music BPM to Delay Milliseconds & LFO Rate CalculatorCalculate audio delay time in milliseconds (ms), reverb pre-delay, and LFO frequency in Hz for whole, half, quarter, 8th, 16th, dotted, and triplet notes.
- Favicon GeneratorMake a favicon from an image, letters or an emoji. A genuine multi-image .ico, the small modern icon set, and four lines of HTML instead of eighteen.
Text & Language (12)
- Word CounterCount words, characters, sentences, and paragraphs in your text. Estimate reading time. Free word counter — no signup required.
- Case ConverterA case converter for every case at once — sentence, title (AP and Chicago), camelCase, PascalCase, snake_case, kebab-case — updating as you type.
- Lorem Ipsum GeneratorA lorem ipsum generator using the real 186-word Cicero vocabulary: paragraphs, sentences, words or list items, optional HTML tags, live word count.
- Character CounterCounts what you actually see, not UTF-16 units — so an emoji counts as one, not two. Includes X's weighted count, real SMS encoding limits, and the byte size.
- Readability Score CheckerA readability checker scoring Flesch Reading Ease, Flesch–Kincaid, Gunning Fog and Coleman–Liau — and listing the sentences that produced the score.
- Words to Pages CalculatorConvert word count to exact document page count. Customize single/double spacing, font size (10pt, 12pt), font family, and reading times. 100% free.
- Duplicate Line RemoverRemove duplicate lines from text, email lists, and code instantly. Options for case matching, alphabetical sorting, and whitespace trimming.
- Text Reverser & Flip ToolReverse text, flip word order, invert line sequence, or generate upside-down unicode text. Instant browser tool with 1-click clipboard copy.
- Keyword Density & Frequency CheckerA keyword density checker for 1-, 2- and 3-word phrases that shows what a page is actually about. No search engine publishes a density target.
- English Dictionary & Audio PronunciationDictionary lookup for English words: definitions, parts of speech, IPA phonetics, example sentences and audio pronunciation, sourced from Wiktionary.
- Rhyme, Synonym & Antonym FinderFind perfect rhymes, near rhymes, synonyms, and antonyms for songwriting, poetry, and creative writing. Powered by the Datamuse lexical API.
- Speech Duration & Reading Time by WPM Pace CalculatorEstimate spoken presentation duration and silent reading time based on word count and words per minute (WPM) speaking delivery pace (110–350 WPM).
AI-Powered Tools (2)
- AI Sentiment AnalyzerA sentiment analyzer scoring −100 to +100 sentence by sentence, so a mixed review reads as mixed. Runs in your browser; the text is never uploaded.
- Background RemoverA background remover for portraits, running in your browser at full resolution. No credits, no account, no upload. Transparent, white or blue backdrop.
Image & Media (16)
- QR Code GeneratorGenerates QR codes entirely in your browser — nothing is uploaded. Static and permanent, so they never expire, need no account, and carry no tracking redirect.
- Color Palette GeneratorSeven harmonies built in HSL, with the contrast ratio and pass/fail on each color — so a palette that cannot carry text is caught now, not during an audit.
- Aspect Ratio CalculatorCalculate aspect ratios and scale image and video dimensions proportionally without distortion. Supports 16:9, 9:16 (TikTok/Reels), 4:3, and 1:1 presets.
- Target Aspect Ratio Pixel Crop Dimension CalculatorCalculate target cropped pixel dimensions (width × height) and sensor pixel retention percentages for 16:9, 4:3, 1:1, 9:16, and 21:9 aspect ratios.
- Image CompressorAn image compressor for JPG, PNG and WebP to an exact file size or by quality. Runs in your browser — nothing is uploaded. Batch, EXIF removed.
- Image ResizerAn image resizer by pixels, percentage, inches or millimeters at a chosen DPI, with presets for Instagram, YouTube, passport and print. In-browser.
- Image ConverterConvert between JPG, PNG and WebP with control over the background color behind transparency. Batch, size comparison, and nothing is uploaded to a server.
- PNG to JPG ConverterConvert PNG to JPG in your browser, choosing the color that replaces transparency instead of getting a black box. Batch, size comparison, nothing uploaded.
- JPG to PNG ConverterConvert JPG to PNG without uploading anything. Honest about what it does and does not do: PNG stops further loss, it cannot undo the loss already in a JPG.
- Signature & Photo ResizerFit a signature or photo to exact pixel dimensions AND a KB range, not just a ceiling. Crops to the ink, cleans the paper, saves JPG. Runs in your browser.
- Image CropperCrop to a locked aspect ratio and set the exact output pixels — in px, inches, cm or mm at any DPI. Warns before it enlarges. Runs in your browser.
- Image to Text (OCR)Extract text from an image in your browser, with a per-word confidence score so you can see where the recognition is shaky. 13 languages, no upload.
- SVG to PNGSVG to PNG at any scale with no loss. Checks first for external fonts, remote images and a missing viewBox — the three things that ruin the output.
- Image Color PickerPick colors from a photo as HEX, RGB and HSL. Samples an area rather than one noisy pixel, averages correctly, and gives the WCAG contrast for text.
- Passport Photo MakerCrop to 35×45 mm, 2×2 in or any size at a chosen DPI, with head-height guides, then lay copies onto a 4×6 or A4 sheet with cut lines.
- QR Code ScannerScan a QR code from your camera or an image and see exactly what it contains. Nothing is opened, joined or dialled automatically, and risky links are flagged.
Weather & Environment (9)
- Weather ForecastWeather lookup for any city worldwide: current conditions and a 7-day forecast from the national meteorological models behind every weather app.
- Sunrise & Sunset CalculatorFind sunrise and sunset times for any location and date. Calculate day length and golden hour. Free tool powered by Sunrise-Sunset API.
- UV Index CheckerCheck the current UV index for any location. Get sun protection recommendations based on UV levels. Powered by Open-Meteo API. Free — no signup.
- Air Quality Index (AQI) & PM2.5 CheckerAn air quality checker for any city: real-time US AQI with the PM2.5, PM10, ozone and nitrogen dioxide readings behind it, and what the index hides.
- Moon Phase & Lunar Calendar TrackerA moon phase tracker showing the current phase, illumination percentage, lunar age, and the exact countdown to the next Full Moon and New Moon.
- Altitude & Elevation FinderFind the ground elevation and altitude in feet and meters for any city, landmark, or mountain peak worldwide. Powered by Open-Meteo Elevation API.
- Heat Index & Real-Feel CalculatorA heat index calculator running the full NWS procedure, including the low-humidity and high-humidity corrections most calculators skip.
- Wind Chill Index & Frostbite Risk CalculatorA wind chill calculator using the 2001 NWS index, with frostbite times — and what wind chill is not: it never changes the temperature of anything.
- Dew Point, Wet Bulb & Psychrometrics CalculatorGet dew point, wet bulb, frost point and absolute humidity, the pressure dew point in ppm for compressed air, and the surface temperature mold starts at.
Data & Reference (6)
- Country Information LookupCountry info for 250 countries and territories — population, capital, area, currencies, languages, calling code, borders and flag. Bundled, not fetched.
- Joke GeneratorGet random jokes in multiple categories — programming, puns, dark humor, and more. Free joke generator powered by JokeAPI. No signup required.
- Trivia Quiz GeneratorTest your knowledge with random trivia questions. Choose category, difficulty, and question count. Powered by Open Trivia DB. Free — no signup.
- ZIP Code & Postal Code LookupFind city names, states, counties, latitude, and longitude coordinates from any US or international postal code. Instant verification tool.
- World Clock & Global Timezone ConverterA world clock converter across 12 major cities, with offsets shown to the minute because not every zone is a whole hour and DST dates do not align.
- Name Origin, Nationality & Age PredictorDiscover the most probable nationality, country of origin, and median age associated with any first name using global demographic data.
Health & Fitness (18)
- TDEE & Calorie CalculatorA TDEE calorie calculator using Mifflin-St Jeor for BMR, with targets for loss, maintenance or gain — and how wide the activity multiplier error is.
- Daily Water Intake CalculatorHow much water to drink daily by weight, exercise and climate — and the part other calculators miss: the official figure counts water in food too.
- Macro & Calorie Deficit CalculatorDaily protein, carb and fat targets from the Mifflin-St Jeor equation — and the only calculator that checks your split against the official IOM ranges.
- US Navy Body Fat CalculatorEstimate body fat from a tape measure with the US Navy formula, cross-checked against the BMI method — and see the ±5.2 point error range studies found.
- Ideal Body Weight (IBW) CalculatorAn ideal body weight calculator comparing all four formulas plus adjusted body weight — and why they disagree by up to 12 kg at tall heights.
- Target Heart Rate CalculatorGet your five training zones from a max heart rate formula that is actually validated — plus why 220 minus your age is wrong, and by how much at your age.
- Intermittent Fasting Tracker & TimerTrack your daily intermittent fast with live countdown timer, 16:8, 18:6, 20:4 protocol presets, and biological metabolic stages (Ketosis, Autophagy).
- Sleep Cycle & Bedtime CalculatorA sleep calculator built on real 90–110 minute cycles, with the hours the AASM recommends by age and a flag on any option under 7 hours.
- Lean Body Mass (LBM) CalculatorA lean body mass calculator running three published equations, with the James formula dropped automatically past the weight where it reverses.
- Calorie Burned Activity CalculatorA calorie burn calculator for 30+ activities using standard MET values — plus the number others omit: how much you would have burned anyway.
- Pregnancy Due Date CalculatorCalculate your estimated baby due date, current gestational age in weeks and days, and pregnancy trimester timeline using Naegele’s rule. 100% free.
- Blood Pressure Category CheckerA blood pressure checker that averages your readings the way the AHA asks, compares both arms, and sizes your cuff. The wrong cuff reads 19.5 mmHg high.
- Running Pace & Split CalculatorA running pace calculator for km and mile splits, treadmill speed, and race predictions that use Riegel's formula rather than flat 5K pace.
- Alcohol Units, BAC Clearance & Calories CalculatorCalculate standard alcohol units, pure ethanol grams, drink calories, and estimated biological body clearance hours from beverage volume and ABV %.
- Workout Sweat Rate & Electrolyte CalculatorCalculate hourly fluid loss sweat rate (L/hr), percentage dehydration, and sodium electrolyte replacement requirements from pre and post-workout body weight.
- Sleep Debt Deficit & Circadian Recovery CalculatorCalculate your cumulative weekly sleep debt deficit and generate an optimal circadian-friendly gradual recovery schedule without causing social jet lag.
- UV Index & Safe Vitamin D Sun Exposure TimerCalculate safe sunlight exposure time in minutes for optimal Vitamin D synthesis (1,000–2,000 IU) based on UV Index and Fitzpatrick skin phototype.
- Jet Lag Circadian Shift & Recovery PlannerBeat jet lag with a pre-flight sleep shift plan. Get day-by-day bedtime adjustments and light exposure timing for your route and direction of travel.
Education (16)
- College & High School GPA CalculatorSemester, cumulative and weighted GPA in one place — with AP and honors bumps, pass/fail exclusions, and a note on the A+ scale difference that trips people up.
- Pomodoro TimerA 25/5 Pomodoro timer with custom intervals, automatic long breaks and an alarm, driven by the system clock so it stays accurate in a background tab.
- Stopwatch & Countdown TimerA stopwatch timer with laps and countdown, driven by the system clock so it stays accurate in a background tab. Full screen, spacebar, alarm.
- Test Grade Percentage CalculatorCalculate test score percentages, letter grades (A+ to F), and GPA equivalents based on questions missed. View full grading scale chart instantly.
- Final Grade CalculatorCalculate the exact minimum score you need on your final exam to pass your class or earn your target letter grade (A, B, C). 100% free student tool.
- Roman Numeral ConverterConvert numbers and dates to Roman numerals and back — and unlike most converters, it rejects invalid numerals like IIII, VX and IC instead of guessing.
- Book & ISBN Search ExplorerISBN book lookup in the Open Library catalogue — title, authors, publisher, date, pages, subjects and cover — with the check digit validated first.
- World Flags & Capital Cities QuizA country flag quiz drawn from the 193 UN member states: half flags, half capitals, ten fresh questions a round with real flag images, not emoji.
- Interactive Periodic Table of ElementsA periodic table explorer: search any element by name, symbol or atomic number for its atomic weight, group, period and electron configuration.
- Kinematic Velocity & Motion CalculatorSolve classical physics kinematic motion equations. Calculates final velocity (v = v₀ + at), displacement distance (d), and average speed. 100% free.
- Ohms Law & Electrical Power CalculatorEnter any two of voltage, current, resistance or power and get the other two — plus the resistor wattage rating you need so the part does not burn out.
- 4-Band Resistor Color Code DecoderA resistor color code calculator that runs both ways: bands to ohms, and the colors for 1k, 10k and 100k — plus which values actually exist.
- Morse Code TranslatorA Morse code translator both ways using the complete ITU alphabet, with real-timing audio, adjustable speed and prosigns. Unknown characters are reported.
- English Text to Grade 1 Braille TranslatorConvert English letters, numbers, and punctuation marks into standard Grade 1 Unicode tactile Braille patterns with 1-click clipboard copy.
- pH Scale & Hydrogen Ion [H+] Concentration CalculatorpH from concentration, molarity or Ka — with the temperature caveat every other calculator omits: pH + pOH = 14 is true only at 25°C.
- Musical Note Pitch to Audio Frequency (Hz) FinderConvert musical note pitch and octave numbers to equal temperament frequency in Hertz (Hz), MIDI key number, and sound wavelength. With audio tone playback.
Business (18)
- Profit Margin CalculatorA profit margin calculator for gross margin, markup, net profit and breakeven — plus the price that hits a target margin, which is not a markup.
- Invoice GeneratorCreate professional invoices instantly online with taxes, custom currencies, and dynamic line items. Print or save directly to PDF. No signup required.
- Discount CalculatorA discount calculator for stacked "extra % off" deals that compound rather than add, sales tax, and both reverse questions: original price and % off.
- UTM Campaign URL BuilderBuild custom campaign tracking URLs with standard UTM parameters for Google Analytics, Meta Ads, TikTok, and Email. 100% free with presets.
- Sales Commission CalculatorCalculate total sales commission, over-quota accelerators, base salary, and on-target earnings (OTE) with interactive quota tracking. 100% free.
- Breakeven Point CalculatorA breakeven calculator for units and revenue from fixed costs and contribution margin, plus margin of safety and how discounting moves the number.
- Return on Investment (ROI) CalculatorCalculate return on investment and the annualized rate that makes different holding periods comparable. A 50% return over 10 years is only 4.1% a year.
- PayPal Fee CalculatorA PayPal fee calculator for goods and services (3.49% + $0.49) and friends and family, the 1.5% international and 4% conversion charges, and the reverse solver.
- Stripe Fee CalculatorCalculate Stripe credit card processing deductions (2.9% + 30¢), international card fees, and net payout revenue. Free tool for SaaS and ecommerce.
- Markup CalculatorCalculate retail selling price, dollar profit, and understand the difference between Markup % and Gross Profit Margin %. 100% free pricing tool.
- CPM (Cost Per Mille) CalculatorA CPM calculator that solves all three ways: cost per thousand impressions from a bill, the budget for a reach target, or the reach from a budget.
- A/B Test Significance CalculatorAn AB test calculator for significance: p-value, Z-score, the confidence interval on the difference, observed power, and the sample size to plan.
- CTR (Click-Through Rate) CalculatorA CTR calculator for ads and organic search, compared against a cited benchmark for your channel and industry rather than a bare good/bad verdict.
- Customer Lifetime Value (LTV) CalculatorCalculate Customer Lifetime Value (LTV / CLV), gross profit LTV, and LTV-to-CAC health ratio for SaaS, subscription, and ecommerce businesses.
- Freelance Hourly Rate CalculatorA freelance rate calculator for hourly and day rates from your target take-home, overheads, tax and realistic billable hours — a floor, not a price.
- Discounted Cash Flow (DCF) CalculatorCalculate the intrinsic fair value of a company or stock using a 5-year Discounted Cash Flow (DCF) model with terminal value and WACC discount rate.
- Affiliate Marketing Commission & EPC CalculatorAn affiliate commission calculator for monthly earnings, earnings per click (EPC) and revenue from your traffic, conversion rate and order value.
- SaaS Subscription MRR & ARR CalculatorCalculate software-as-a-service Monthly Recurring Revenue (MRR), Annual Recurring Revenue (ARR), logo churn rate, and Customer Lifetime Value (LTV).
PDF Tools (9)
- Merge PDFCombine PDFs into one file without uploading them anywhere. Set the order, see page counts, flatten form fields. Runs entirely in your browser.
- Split PDFExtract a page range, delete pages, or split a PDF into separate files. Multiple files come back as one ZIP. Nothing is uploaded — it all runs in your browser.
- JPG to PDF ConverterTurn JPG, PNG and WebP images into a single PDF. Page size matched to each image or set to A4 or Letter, auto orientation, margins. Nothing is uploaded.
- PDF to JPG ConverterTurn PDF pages into JPG, PNG or WebP at a resolution you choose, with the output pixel size shown before you convert. Runs in your browser; nothing is uploaded.
- Rotate PDFTurn PDF pages 90, 180 or 270 degrees and save the rotation into the file. Adds to any rotation a scanner already applied. Nothing is uploaded.
- Compress PDFShrink a PDF to an exact target size, and be told first whether it is a scan (safe) or real text (you lose the text layer). Runs in your browser.
- Watermark PDFStamp text across every page or a selection: diagonal or straight, any size, opacity and color. Drawn into the page so it prints. Nothing is uploaded.
- Add Page Numbers to PDFNumber a PDF with the position and format you want, skipping a cover and starting from any number. The "of N" counts numbered pages, not sheets.
- PDF to TextPull the real text out of a PDF with paragraphs rebuilt from the document’s own line spacing. Tells you when a PDF is a scan instead of returning nothing.