Online Stopwatch with Laps
Start, lap and stop with one key. Every lap shows its own time and the running total, with the fastest and slowest marked.
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Spacestart or stopLlapRresetFfull screenMlap sound
Sound on each lap
How this works: 1 source, Checked against 1 worked example,
How this works
How it’s tested
One worked example for this page is checked by automated tests before every release: given the inputs, the tool must show the expected answer.
Privacy
On your device. Nothing you enter or open leaves this browser. About privacy labels
Changes
- Added 10, 20, 30, 45 and 90 second timer pages, each with its own uses, a table and cited facts.
- A timer opened from a link no longer resets on reload, a tap brings the sound back after one, and on phones Start is on the first screen.
- First published.
Laps, splits and timing things accurately
A lap time is how long one stretch took; a split is the total on the clock when that stretch ended. Run four laps of a track in 1:52, 1:49, 1:55 and 1:47 and your splits are 1:52, 3:41, 5:36 and 7:23. This stopwatch records both: press Lap at the end of each stretch and the list shows each lap next to the running total, with the fastest and slowest picked out.
It is handy well beyond the track: a swimmer’s lengths, how long a bus journey or a queue really takes, a speech rehearsal, a child reading a passage aloud, or a reaction-time game between friends. The time comes from timestamps taken when you press the buttons, not from counting ticks, so it doesn’t drift when you switch tabs or the browser slows its timers in the background. Press Reset to clear the laps and start again, or keep the list and copy the times down before you do.
- Browsers slow down hidden pages to save power: since Chrome 88, timers in a page that has been hidden for more than five minutes can be checked as rarely as once a minute. A stopwatch that counted its own ticks would fall behind; this one reads the clock instead. Source: Chrome for Developers, Heavy throttling of chained JS timers (Chrome 88).
Stopwatch times as decimal hours
For timesheets and invoices, which bill in tenths or hundredths of an hour: 6 minutes is 0.1 h, 15 minutes is 0.25 h.
| Stopwatch reading | Decimal hours | Minutes |
|---|---|---|
| 1:00 | 0.017 | 1 |
| 3:00 | 0.05 | 3 |
| 5:00 | 0.083 | 5 |
| 6:00 | 0.1 | 6 |
| 10:00 | 0.167 | 10 |
| 12:00 | 0.2 | 12 |
| 15:00 | 0.25 | 15 |
| 18:00 | 0.3 | 18 |
| 20:00 | 0.333 | 20 |
| 24:00 | 0.4 | 24 |
Show all 21 rowsShow fewer
| 30:00 | 0.5 | 30 |
| 36:00 | 0.6 | 36 |
| 40:00 | 0.667 | 40 |
| 45:00 | 0.75 | 45 |
| 48:00 | 0.8 | 48 |
| 50:00 | 0.833 | 50 |
| 54:00 | 0.9 | 54 |
| 1:00:00 | 1 | 60 |
| 1:15:00 | 1.25 | 75 |
| 1:30:00 | 1.5 | 90 |
| 2:00:00 | 2 | 120 |
Frequently Asked Questions
What is the difference between a lap and a split?
A lap is the time for one section on its own; a split is the total elapsed time at the end of that section. If your first two laps are 45.2 and 47.8 seconds, the splits are 45.2 and 1:33.0. Laps show your pacing; splits compare against a target.
Does the stopwatch keep running if I lock my phone?
It keeps time, because it works from the moment you pressed Start rather than counting ticks. If the phone pauses the browser while locked, the display simply catches up when you come back and the reading is still right. Laps can only be marked while the page is open.
How precise is an online stopwatch?
The display shows hundredths of a second and the timing comes from your device’s clock, so it is very consistent. The weak link is the finger on the button: human reaction time is far longer than a hundredth, which is why races decided by fractions of a second use electronic timing.