What this stopwatch does
This is a straightforward, no-frills online stopwatch: press Start and it counts up from zero, in hours, minutes, seconds and hundredths, until you press Pause. While it's running you can press Lap as many times as you like to capture split times without interrupting the count, and Reset zeroes everything and clears the lap list.
It's built for the moments where you just need an accurate running clock — timing a workout interval, a presentation rehearsal, a recipe step, or how long a task actually took — without installing an app or hunting for a physical stopwatch.
How to use it
Four buttons, no setup — press Start and you're timing.
- Press Start.The clock begins counting up immediately in hours, minutes, seconds and hundredths.
- Record a lap.While it's running, press Lap to capture a split without interrupting the count. Repeat as many times as you like.
- Pause and resume.Press Pause to freeze the clock, then Start again to pick up exactly where you left off.
- Reset when you're done.Press Reset to zero the clock and clear every lap, ready for the next run.
How it works
The stopwatch reads a timestamp from your browser's high-resolution clock the instant you press Start, then subtracts that timestamp from the current one on every screen refresh to get the elapsed time — the same subtraction a physical stopwatch does mechanically. Pausing simply stores the elapsed total and stops the subtraction; pressing Start again begins a new segment that gets added on top, so nothing is lost.
Each lap works the same way: its total is the elapsed time at the moment you pressed Lap, and its split is that total minus the previous lap's total — in other words, how long that particular segment took on its own.
00:00:12.34 total → split 00:00:12.34Lap 2 at
00:00:25.10 total → 25.10 − 12.34 = split 00:00:12.76Lap 3 at
00:00:40.00 total → 40.00 − 25.10 = split 00:00:14.90
Quick examples
The lap splits from the worked example above, laid out the way the tool displays them.
| Lap | Total time | Split |
|---|---|---|
| 1 | 00:00:12.34 | 00:00:12.34 |
| 2 | 00:00:25.10 | 00:00:12.76 |
| 3 | 00:00:40.00 | 00:00:14.90 |
Timing something with a fixed budget instead — a talk slot, a study block, a cooking step? The countdown timer counts down to zero and alerts you, and the interval timer cycles automatically between work and rest periods.
Who uses it, and for what
- Runners & athletes timing a workout or comparing lap splits across an interval session.
- Cooks & bakers tracking how long a step actually takes without a kitchen timer to hand.
- Teachers & presenters keeping an eye on how long a talk, activity or exam has run.
- Developers & testers manually timing how long a process or task takes to complete.
- Anyone tracking time — study sessions, chores, hobbies, or simple curiosity.
If your goal is a fixed work/rest cycle rather than open-ended timing, the interval timer and Pomodoro timer handle that structure for you.
Frequently asked questions
How accurate is this online stopwatch?
The stopwatch reads your device's high-resolution clock and updates the display roughly every frame (about 60 times a second), so it's accurate to the nearest hundredth of a second for as long as the browser tab stays active. It isn't intended for scientific timing that needs lab-grade precision.
Will the stopwatch keep running if I switch tabs or lock my phone?
Most browsers slow down or pause timers in background tabs to save battery, so the on-screen number may stop updating while you're away. When you come back the display catches up to the correct elapsed time, because it's calculated from a clock timestamp rather than by counting ticks — but for best results keep the tab open while timing something important.
Can I record lap or split times?
Yes. While the stopwatch is running, press Lap to record the current time without stopping the clock. Each lap shows both its split (time since the previous lap) and its total (time since Start), and you can keep lapping as many times as you like.
Does this stopwatch save my times or require an account?
No. There's no sign-up and nothing is uploaded — the stopwatch and its lap list live entirely in your browser tab and disappear if you refresh or close the page. Use Copy or Download CSV before you navigate away if you want to keep a record.
What's the difference between this stopwatch and the countdown timer?
A stopwatch counts up from zero with no end point, which is what you want when you don't know how long something will take. The countdown timer counts down from a time you set and alerts you at zero, which suits a fixed time budget like a presentation slot or a cooking step.
Can I use the stopwatch offline?
Once the page has loaded, the stopwatch runs entirely with JavaScript in your browser and doesn't need an internet connection to keep timing — only the initial page load requires one.
Does refreshing or closing the page reset the time?
Yes. The stopwatch keeps no history between visits, so reloading the page, closing the tab, or navigating away resets the clock and clears any recorded laps.
Accuracy & sources
This stopwatch reads elapsed time directly from your browser's built-in high-resolution clock and does the same subtraction a physical stopwatch does — no proprietary formula, no server round-trip. The worked example above, and the split and total figures in the lap table, were checked by hand against those numbers.
There's no external time-format standard governing a simple stopwatch, so accuracy here comes down to standard time arithmetic and the browser's clock rather than an outside authority; every example on this page was independently verified. Written and reviewed by Fletcher Langley, and re-checked whenever the tool changes — last reviewed August 2026.
About the author
Operations and workforce-systems specialist with 14+ years inside shift-based industries and payroll platforms, and a BS in Industrial Engineering. Fletcher writes and reviews the calculators, converters, and guides here — from overnight-shift math to decimal payroll hours — drawing on years spent translating between 12-hour, 24-hour, and military time for real timesheets.
Written & reviewed by Fletcher Langley · Last updated: August 2026