Image & Color Tools
Image Size Calculator
Calculate responsive image dimensions while maintaining aspect ratio. Perfect for resizing images for web design, social media, and print. Prevent image distortion with accurate calculations.
Use Image Size Calculator to get instant results without uploads or sign-ups. Everything runs securely in your browser for fast, reliable output.
Your results will appear here.
About this tool
Maintaining aspect ratio is crucial when resizing images. If you change width and height independently without considering aspect ratio, images become stretched or squashed, looking unprofessional. Our Image Size Calculator ensures your images scale proportionally, maintaining their original appearance.
Responsive web design requires images to adapt to different screen sizes while keeping their proportions. Whether you're optimizing images for mobile, creating thumbnails, preparing social media graphics, or ensuring retina display compatibility, calculating correct dimensions is essential.
This tool is indispensable for web developers, graphic designers, content creators, and anyone working with images. Instead of guessing dimensions or doing manual math, get instant, accurate calculations that guarantee your images look perfect at any size.
The calculator uses the aspect ratio formula: originalWidth / originalHeight = newWidth / newHeight. This mathematical relationship ensures that when one dimension changes, the other adjusts proportionally, preventing any distortion or letterboxing.
Usage examples
Scale Down for Web
Reduce large photo for website
Original: 3000×2000px New width: 800px Calculated height: 533px Maintains 3:2 aspect ratio
Mobile Responsive
Fit image to mobile width
Original: 1920×1080px New width: 375px (iPhone) Calculated height: 211px Perfect for responsive design
Social Media Sizing
Calculate for Instagram
Original: 4000×3000px New width: 1080px (Instagram) Calculated height: 810px
Thumbnail Creation
Small preview image
Original: 1600×900px New height: 120px Calculated width: 213px
Print to Digital
Convert print dimensions
Original: 8×10 inches (2400×3000px at 300dpi) Calculations preserve ratio for web
How to use
- Enter your original image width and height in pixels.
- Choose whether to set a new width OR new height.
- The calculator automatically computes the missing dimension.
- Aspect ratio is maintained to prevent distortion.
- Use calculated dimensions for responsive design.
- Perfect for CSS, HTML img tags, and design software.
Benefits
- Calculate image dimensions instantly
- Maintain aspect ratio automatically
- Prevent image distortion and stretching
- Perfect for responsive web design
- Essential for social media graphics
- Save time with automatic calculations
- No manual math required
- Works for any image size
- Useful for thumbnails and previews
- Critical for professional designs
- Free and works offline
- Essential tool for designers and developers
FAQs
What is aspect ratio?
Aspect ratio is the proportional relationship between an image's width and height, expressed as width:height (like 16:9 or 4:3). It determines the image's shape. When resizing, maintaining aspect ratio prevents distortion by keeping width and height proportional to the original.
Why do my images look stretched or squashed?
Images look distorted when you change width and height independently without maintaining aspect ratio. For example, a 800×600px (4:3 ratio) image forced to 800×400px (2:1 ratio) will look squashed vertically. Always calculate proportional dimensions to preserve the original appearance.
How do I resize images for responsive web design?
For responsive design, calculate dimensions for your target screen width while maintaining aspect ratio. For mobile (375px), desktop (1920px), and tablet (768px), calculate proportional heights. In CSS, use max-width: 100%; height: auto; to let images scale naturally within containers.
What are common aspect ratios?
Common ratios include: 16:9 (widescreen, HD video, modern monitors), 4:3 (standard, older screens), 1:1 (square, Instagram), 3:2 (DSLR photos), 21:9 (ultrawide), 9:16 (vertical mobile video). Each serves different purposes in design and media.
Should I upscale or downscale images?
Downscaling (reducing size) is safe and maintains quality. Upscaling (increasing size) can cause blurriness and pixelation because you're adding pixels that don't exist in the original. Always work from high-resolution originals and downscale to needed sizes. Never upscale beyond 120% of original.
How do I calculate dimensions for retina displays?
Retina displays have 2x or 3x pixel density. For a 400×300px display area on retina, you need an 800×600px image (2x) or 1200×900px (3x). Use this calculator to determine the @2x or @3x dimensions while maintaining aspect ratio.
What about social media image sizes?
Social platforms have specific size requirements: Instagram posts (1080×1080 square or 1080×1350 portrait), Facebook posts (1200×630), Twitter (1200×675), LinkedIn (1200×627). Use this calculator to resize your originals to these dimensions while maintaining aspect ratio (may require cropping).
Can I calculate dimensions in inches or centimeters?
Yes! The calculator works with any unit (pixels, inches, centimeters, etc.) as long as width and height use the same unit. For print, use DPI to convert: at 300 DPI, an 8×10 inch image = 2400×3000 pixels. Calculate proportions in whichever unit you prefer.
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