🍅 Pomodoro Timer
A 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.
0 pomodoros completed
Timing runs from the system clock, so it stays accurate if you switch tabs.
What Pomodoro Timer Does
The Pomodoro Technique is one rule with a timer attached: work on a single task for 25 minutes without interruption, then take a 5-minute break, and after four rounds take a longer one. Francesco Cirillo worked it out as a student in the late 1980s using a tomato-shaped kitchen timer, which is where the name comes from — pomodoro is Italian for tomato.
What makes it work is not the 25 minutes. It is that the interval is short enough to start without dread and fixed enough that the end is visible from the beginning. Most procrastination is a starting problem rather than a stamina problem, and committing to 25 minutes is a much smaller ask than committing to an afternoon.
There is a technical problem specific to browser-based Pomodoro timers, and most of them have it. Browsers throttle JavaScript timers in background tabs — and switching tabs during a focus session is completely normal. A timer that counts seconds therefore runs long: measured, a 25-minute session finishes at 26 minutes under a mild clamp and at 50 minutes under a heavy one. This one stores a deadline and reads the system clock, so backgrounding delays the display and nothing else.
The rest of this page answers the two questions Google says people actually ask about the technique — whether it is 20 or 25 minutes, and whether 25/5 beats 50/10 — rather than restating the rules and stopping.
How to Use Pomodoro Timer
- Pick one task and start a 25-minute focus interval
- Work on only that task until the alarm — note any interruption rather than switching to it
- Take the 5-minute break away from the screen; the next interval starts automatically
- After four pomodoros, take the longer break the timer offers
Formula Used by Pomodoro Timer
The standard cycle
4 × (25 min focus + 5 min break) + one long break of 15–30 min
- Pomodoro
- One 25-minute focus interval, treated as indivisible
- Long break
- After every fourth pomodoro, away from the desk
Worked example
One full cycle
- 4 × 25 = 100 minutes of focused work
- 3 × 5 = 15 minutes of short breaks
- Plus one long break of 15
Result: 130 minutes elapsed for 100 minutes of work — a 77% duty cycle
Comparing the common ratios
duty cycle = focus ÷ (focus + break)
- Why it matters
- It shows the ratios are closer than they look; what differs is interruption frequency
Worked example
The three usual schemes
- 25/5 → 25 ÷ 30 = 83.3%
- 50/10 → 50 ÷ 60 = 83.3%
- 52/17 → 52 ÷ 69 = 75.4%
Result: 25/5 and 50/10 have an identical duty cycle. The choice is about how often you restart, not how much you rest
Why a deadline rather than a countdown
remaining = deadline − now
- deadline
- A timestamp fixed when the interval starts
- The alternative
- remaining = remaining − 1 on each tick, which drifts under throttling
Worked example
A 25-minute focus interval in a backgrounded tab
- Tick-counting at a 2 s clamp: 1,500 ticks × 2 s = 50 min
- Deadline: the timestamp does not move
Result: 25 minutes exactly, however aggressively the browser throttles
The common interval schemes
Duty cycle is the share of elapsed time spent working. Note that the two most-debated schemes are identical on that measure — they differ in how often you pay the cost of resuming.
| Scheme | Focus | Break | Duty cycle | Suits |
|---|---|---|---|---|
| Classic Pomodoro | 25 min | 5 min | 83.3% | Fragmented tasks, trouble starting, study |
| Extended | 50 min | 10 min | 83.3% | Writing, coding, anything with a long warm-up |
| Long form | 90 min | 20 min | 81.8% | Deep work, aligned with ultradian rhythm claims |
| DeskTime observation | 52 min | 17 min | 75.4% | Reported from tracking data, not a designed scheme |
| Short form | 15 min | 3 min | 83.3% | Very low starting energy, heavy resistance |
What background throttling costs a tick-counted timer
A 25-minute focus interval measured by decrementing a counter each tick. Switching tabs is normal during a pomodoro, which is what makes this the defect that matters here.
| Tab state | Effective tick | Session actually ends at | Late by |
|---|---|---|---|
| Foreground | 1.00 s | 25.0 min | — |
| Background, mild clamp | 1.04 s | 26.0 min | 1 minute |
| Background, heavy throttle | 2.00 s | 50.0 min | 25 minutes |
| Deep throttle or power saving | 5.00 s | 125.0 min | 100 minutes |
| Deadline-based (this tool) | irrelevant | 25.0 min | never |
Cirillo's original rules
The technique is stricter than most apps implement. The rules exist to make interruptions visible rather than to be obeyed perfectly.
| Rule | What it means in practice |
|---|---|
| A pomodoro is indivisible | If it is broken, it does not count — you restart rather than resume |
| One task per pomodoro | Switching tasks mid-interval defeats the point |
| If it takes more than 5–7, split it | A task needing three hours should be broken into smaller pieces first |
| If it takes less than one, combine | Batch small tasks into a single interval |
| Record interruptions | Note them and continue; the log is the useful output |
| The next pomodoro will go better | Cirillo's own framing — a bad interval is data, not failure |
How to Read Your Result
25 minutes is arbitrary, and that is fine
There is no research establishing 25 as an optimum. Cirillo picked it because it was what his kitchen timer conveniently did and it felt short enough to commit to. The number matters far less than the two properties it has: short enough that starting is easy, and fixed so that the end is knowable in advance. If 25 does not fit your work, change it — the timer here lets you. What you should not do is treat the number as though it were derived from something.
25/5 against 50/10 comes down to restart cost
Their duty cycles are identical at 83.3%, so the rest you get is the same. What differs is how often you pay the cost of resuming. Tasks with a long warm-up — writing prose, holding a codebase in your head, working through an argument — lose real time at every restart, and being interrupted at 25 minutes can throw away most of the interval. Fragmented or aversive tasks benefit from the opposite: the frequent finish lines are the point. Pick by the shape of the work, not by which sounds more disciplined.
The break is the part people get wrong
Spending the five minutes on the same screen, reading a feed, does very little. The break is meant to be a change of mode: stand, look at something more than six meters away, get water, move. Screen-based rest reportedly restores attention much less than physical or visual change, and it also risks becoming a twenty-minute break. Setting the timer to auto-advance, as it does here by default, is partly a defense against exactly that.
On ADHD, be careful with the claims
Google lists "Is Pomodoro good for ADHD?" as a common question, and the technique is very widely recommended in that context. The mechanism is plausible — externalizing time, lowering the barrier to starting, making the endpoint visible — and many people report it helps. But the specific research base is thin, and a hard stop mid-flow can be genuinely counterproductive for someone who has just achieved focus. It is reasonable to try, sensible to adapt the intervals, and not a substitute for advice from a clinician who knows your situation.
Where this tool is behind
The leading Pomodoro sites offer ambient audio, visual themes, to-do lists, daily streaks and focus statistics, and Flocus is the strongest of them on design alone. This page has none of that — it is a timer that keeps correct time, advances the cycle, and explains the technique honestly. If what makes you actually use a timer is a lofi soundtrack and a streak counter, one of those tools is the better choice, and that is a reasonable thing to want.
The interruption log is the underrated output
Cirillo's rule to record every interruption rather than act on it is usually treated as an inconvenience and skipped. It is arguably the most useful part. After a week you have a list of what actually breaks your concentration, and it is rarely what you would have guessed — it tends to be a small number of recurring sources rather than random noise. That list is actionable in a way that "I struggle to focus" is not.
Limitations & Accuracy Notes
- This is a timer, not a productivity suite. Ambient audio, themes, task lists, streaks and statistics — which the leading paid tools all offer — are not included.
- Nothing is saved. The completed-pomodoro count resets when you close or reload the page; there is no account and no history.
- The alarm may not sound if the tab is in the background or the device is locked, because browsers suspend audio for hidden pages. The timing stays correct regardless.
- Interval lengths are conventions, not findings. There is no evidence establishing 25 minutes as optimal, and the numbers here are adjustable for that reason.
- Nothing on this page is medical or psychological advice. The technique is a work habit; questions about attention difficulties belong with a qualified clinician.
- The 52/17 figure comes from a company's analysis of its own time-tracking users and is an observation about that sample, not a controlled result.
Frequently Asked Questions
Is a Pomodoro 20 or 25 minutes?
Is 25/5 or 50/10 better?
Does the timer stay accurate if I switch tabs?
Why a long break after four?
Is the Pomodoro technique good for ADHD?
What should I do if I am interrupted mid-pomodoro?
References & Further Reading
- The Pomodoro Technique — official site — Francesco Cirillo’s own site, which stresses that the timer is only the starting point and that the full technique includes daily planning, interruption management and effort estimation
- MDN — Reasons for delays longer than specified (setTimeout) — Documents the background-tab throttling that makes tick-counted timers run long, which is the defect this timer was rewritten to avoid
- Pomofocus — The #1 result for this term, and the benchmark for the customisable-intervals and task-list feature set noted in the limitations