Stopwatch
Stopwatch with split lap timer.
{{ formatMs(watch) }}
| Split | Time | Length |
|---|---|---|
| {{ laps.length - i }} | {{ formatMs(lap.time) }} | {{ formatMs(lap.diff) }} |
What Is an Online Stopwatch?
A stopwatch measures elapsed time, but how useful it is depends largely on whether it can record times for individual segments. This one keeps both the running total from the start (the split) and the interval since the previous record (the lap), which makes it well suited to timing work that runs through several stages.
Timing runs entirely inside your browser, so the records disappear when you close the tab. Keep the tab open for long sessions. There is no export function, so save or screenshot the screen if you want to keep the results.
How to Use the Stopwatch
- Press Start to begin timing Timing starts as soon as you press Start. The moment you press it becomes the baseline, so press it at the same instant the activity begins.
- Record a lap at each break point Pressing Lap adds the interval time and the running total up to that moment to the list. You can record as many laps as you like.
- Press Stop to pause Pressing Stop halts the timer. Press Start again and it continues from where you stopped.
- Press Reset to clear everything Reset clears both the time and the lap list. Save the screen first if you want to keep the records.
Tips for getting more out of it
- Lap time records the elapsed time for each segment; split time records the cumulative time from the start.
- It can also be used for tracking work sessions or the Pomodoro Technique (25 minutes of focus → 5 minutes of rest).
- Closing the browser tab will reset the stopwatch. Avoid closing the tab during long measurement sessions.
- You can save the lap time list by taking a screenshot of the screen.
When an Online Stopwatch Comes in Handy
Timing work stage by stage
Break a sequence of tasks into laps and you get hard numbers on which stage eats the most time — useful when you want to rework a procedure.
Running the Pomodoro technique
For the pattern of 25 minutes of focus followed by a 5-minute break, you can watch the elapsed time and mark each transition.
Logging exercise and training
Take a lap at every interval and you can check afterwards whether your pace dropped between sets.
Managing time while cooking or running experiments
When several stages overlap, you can track how long each one has been running as a split.
Timing Terms Explained
- Lap
- The interval from the previous record to the current one. Use it to see how long a single circuit or a single stage took.
- Split
- The running total since the start. Use it to see how far you have progressed overall.
- Reaction Time
- The gap between recognising a signal and your body beginning to move. In humans it is generally put at 0.2 to 0.25 seconds, and it is the main source of error in hand-operated timing.
- Millisecond
- One thousandth of a second. This unit is shown whenever small margins matter, as with competitive records.
FAQ
Side Note — World Speed Records — Various Speeds Measured with a Stopwatch
What speed do humans perceive as "fast"? Usain Bolt's world record in the 100m sprint, set at the 2009 Berlin World Championships, was 9.58 seconds. His top speed reached 44.72 km/h (about 12.4 m/s).
By comparison, the Tokaido/Sanyo Shinkansen "Nozomi" has a top speed of 285 km/h (about 79.2 m/s) — roughly 6 times faster than Bolt. F1 cars top out at over 370 km/h, the speed of sound (in dry air at 0°C) is about 1,224 km/h, and the speed of light is approximately 1.08 billion km/h (circling the Earth about 7.5 times per second).
In the world of milliseconds, a stopwatch can time the fastest F1 pit stop (Red Bull 2023: 1.80 seconds) and the average human blink (0.15–0.4 seconds). The average human reaction time is about 0.2–0.25 seconds — which is also roughly the "dead time" between a traffic light turning green and pressing the accelerator.
Incidentally, a hummingbird flaps its wings about 50–80 times per second — just 12–20 milliseconds per beat. The natural world is full of remarkable speeds.