⏱️ Online Stopwatch
By ToolNimba Editorial Team · Updated 2026-06-19
| # | Lap time | Split (total) |
|---|
Press Start to begin timing.
This online stopwatch times anything you need, from a workout interval to a presentation rehearsal, right in your browser. Press Start to begin, Lap to record a split without stopping the clock, Stop to pause, and Reset to clear. The display reads minutes, seconds, and hundredths (mm:ss.cc), and your laps are listed with both the individual lap time and the running total.
What is the Online Stopwatch?
A stopwatch measures the time that passes between when you start it and when you stop it, known as elapsed time. Unlike a clock, which tracks the time of day, a stopwatch always begins from zero and counts up. That makes it the right tool whenever you care about a duration rather than a moment: how long a lap took, how many seconds a chemical reaction ran, or how long you spoke.
This tool measures elapsed time with the browser performance clock, which is a high-resolution timer designed for exactly this purpose. Because it counts from a fixed reference point rather than reading the wall clock, the measurement is not thrown off if your system time is adjusted while the stopwatch runs. The reading you see updates many times per second as the display redraws, but the underlying duration is always computed from the difference between the start point and the present moment, so accuracy does not depend on how often the screen refreshes.
The lap feature records a checkpoint while the clock keeps running. Each lap shows two numbers: the lap time, which is how long that single segment took since the previous lap, and the split (or cumulative) time, which is the total elapsed time at the instant you pressed Lap. Athletes use lap times to compare each repetition and splits to see overall pace. Pausing with Stop keeps the accumulated time, so you can resume from where you left off rather than starting over.
When to use it
- Timing workout intervals, rounds, or rest periods, and comparing each repetition with the lap feature.
- Rehearsing a speech or presentation to keep it within an allotted time.
- Timing cooking, brewing, or science experiments where the duration matters more than the clock time.
- Recording split times for running, swimming, or cycling laps without stopping the count.
How to use the Online Stopwatch
- Press Start to begin timing from zero (the spacebar also starts and stops).
- Press Lap to record a split while the clock keeps running.
- Press Stop to pause; the elapsed time is kept so you can Resume later.
- Press Reset to clear the time and the recorded laps back to zero.
Formula & method
Worked examples
You start the stopwatch and stop it after 95.4 seconds.
- Total seconds = 95.4
- Minutes = floor(95.4 ÷ 60) = 1
- Seconds = 95.4 − (1 x 60) = 35.4
- Hundredths = 0.4 x 100 = 40
- Display = 01:35.40
Result: The stopwatch reads 01:35.40
You record three laps at splits of 30.00 s, 65.00 s, and 95.00 s.
- Lap 1 time = 30.00 − 0 = 30.00 s, shown as 00:30.00
- Lap 2 time = 65.00 − 30.00 = 35.00 s, shown as 00:35.00
- Lap 3 time = 95.00 − 65.00 = 30.00 s, shown as 00:30.00
- The split column shows the running totals: 00:30.00, 01:05.00, 01:35.00
Result: Lap times 30.00 s, 35.00 s, 30.00 s with a final split of 01:35.00
How elapsed seconds map to the mm:ss.cc display
| Elapsed time | Minutes | Seconds | Display |
|---|---|---|---|
| 5.25 seconds | 0 | 5.25 | 00:05.25 |
| 59.99 seconds | 0 | 59.99 | 00:59.99 |
| 60 seconds | 1 | 0 | 01:00.00 |
| 95.4 seconds | 1 | 35.4 | 01:35.40 |
| 600 seconds | 10 | 0 | 10:00.00 |
What each stopwatch control does
| Control | Action |
|---|---|
| Start / Stop / Resume | Begins, pauses, or continues the timer (also the spacebar) |
| Lap | Records a split without pausing the clock |
| Reset | Clears the elapsed time and all laps back to zero |
Common mistakes to avoid
- Confusing lap time with split time. The lap time is how long one segment took on its own. The split is the cumulative total at that moment. If your laps are 30 s each, the lap times stay near 30 s while the splits keep climbing (30, 60, 90 and so on).
- Expecting Reset to pause first. Reset clears everything at once, including the laps. If you only want to hold the current reading, use Stop instead, which keeps the time so you can Resume.
- Treating hundredths as milliseconds. The two digits after the dot are hundredths of a second, not thousandths. So 01:35.40 means 1 minute, 35 seconds, and 40 hundredths (0.40 s), not 40 milliseconds.
- Assuming the tab keeps perfect time in the background. Browsers slow down timers in hidden or inactive tabs to save power. The elapsed time is still computed correctly from the start point, but the on-screen number may only catch up when you return to the tab.
Glossary
- Elapsed time
- The duration that passes between starting and stopping the stopwatch, always counted up from zero.
- Lap time
- How long a single segment took, measured from the previous lap to the moment you press Lap.
- Split time
- The cumulative elapsed time at the instant a lap is recorded, also called the total or running time.
- Hundredths
- The two digits after the decimal point in mm:ss.cc, each representing one hundredth (0.01) of a second.
- Resume
- Continuing the stopwatch after a Stop, adding to the time already counted rather than starting over.
Frequently asked questions
How accurate is this online stopwatch?
It measures elapsed time using the browser high-resolution performance clock, which is precise to a fraction of a millisecond and unaffected by changes to your system clock. The display shows hundredths of a second. Real-world accuracy is limited mostly by human reaction time when pressing Start and Stop, which is typically around 0.2 seconds.
What does mm:ss.cc mean?
It is minutes, seconds, and hundredths of a second. For example, 02:09.75 means 2 minutes, 9 seconds, and 75 hundredths (0.75) of a second. The format keeps the reading compact while still showing fine detail.
What is the difference between a lap and a split?
A lap time is how long one segment took on its own, measured from the previous lap. A split is the total elapsed time at the moment you pressed Lap. This stopwatch shows both, so you can compare each segment and track your overall pace.
Does the stopwatch keep running if I switch tabs?
The underlying timing keeps measuring from the start point, so the elapsed time stays correct. However, browsers throttle timers in background tabs to save power, so the visible number may pause updating and then jump to the right value when you return to the tab.
Can I pause and resume without losing my time?
Yes. Pressing Stop pauses the clock but keeps the accumulated time. Pressing Start again (it reads Resume after a stop) continues counting from where you left off. Only Reset clears the time back to zero.
Is my data sent anywhere?
No. The stopwatch runs entirely in your browser with plain JavaScript. Nothing is uploaded, stored on a server, or saved between sessions, so reloading the page clears everything.