Stopwatch
A simple accurate stopwatch for timing anything.
Stopwatch
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What Is the Stopwatch?
A stopwatch measures elapsed time from a start signal to a stop, with lap and split recording for intervals along the way. Precision timing matters across sports training, cooking, workouts, experiments, presentations, and any process where duration reveals something. The difference between a stopwatch and a clock is direction: clocks answer what time is it, while stopwatches answer how long did it take, capturing only the span you care about. This tool runs in your browser with millisecond display, lap memory you can review after stopping, and controls tuned for keyboard use so starting on a cue feels immediate.
Key Statistics
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Hundredths
Precision level required for official swimming timing
Source: World Athletics and FINA timing standards
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Lap versus split
Laps show individual interval times while splits show cumulative elapsed time
Source: Timing convention
The Formula
Elapsed time using system clock.
Worked Examples
Start the stopwatch when you begin a task and pause it to check elapsed time, then resume without resetting. Use the lap feature to record split times for each mile of a run or each section of a long meeting. Reset to zero between separate activities like tracking multiple workout sets.
Interval training session
- Start the watch as the first sprint begins
- Tap lap at each sprint finish to log that interval
- Stop after the final repetition
Each lap entry shows one effort so you can compare fatigue across sets.
Real World Use Cases
Workout timing
Time intervals, rest periods, and planks without watching a clock face.
Cooking precision
Track searing, blanching, and steeping times that make or break recipes.
Productivity experiments
Measure how long tasks actually take to calibrate future planning.
Expert Tips
- ✓ Learn the lap key position by touch so your eyes stay on the event being timed.
- ✓ For human reaction limited starts, remember measured times include your reaction delay of roughly two tenths of a second.
- ✓ Record laps even when unsure; reviewing splits after stopping beats trusting memory.
- ✓ Keep sessions comparable by starting each attempt the same way relative to the signal.
Frequently Asked Questions
How do I use a stopwatch? ▼
Press start to begin timing, press stop to freeze the time, and press reset to clear it. The lap button records intermediate times without stopping the clock.
What is the difference between a stopwatch and a timer? ▼
A stopwatch counts up from zero to measure elapsed time, while a timer counts down from a set duration to zero. Use a stopwatch to measure how long something takes and a timer to set a limit.
How do I record lap times? ▼
Press the lap button each time a segment ends. It records the time for that segment while the main clock keeps running, so you can compare each lap against the others.
What is the difference between a split and a lap? ▼
A split shows the total elapsed time up to that moment, and a lap shows the time for just that segment since the previous lap. Many stopwatches let you read either.
How accurate is an online stopwatch? ▼
It depends on your device clock, but for most purposes it is accurate to a fraction of a second. Use the lap feature to check consistency across practice runs.
Can I use this stopwatch on my phone? ▼
Yes. It runs in any mobile browser and works just like a dedicated app, with start, stop, lap, and reset controls, and no installation required.
What is a split time? ▼
A cumulative reading at any checkpoint during an ongoing measurement, showing total elapsed duration to that point.
How accurate is a browser stopwatch? ▼
Accurate to within milliseconds for practical purposes, though display refresh introduces tiny visual latency.
Common Mistakes to Avoid
- ⚠ Pressing reset instead of pause between laps. Reset clears the entire session and all split times, losing every lap recorded so far. Use the lap button to record segments and pause to stop without losing data.
- ⚠ Confusing lap and split readings when reviewing times. A lap measures the duration of the most recent segment, while a split shows total elapsed time since start. Comparing a lap against a split gives misleading results.
- ⚠ Letting the stopwatch run in a background browser tab during long sessions. Browsers throttle inactive tabs, causing the displayed time to drift behind real elapsed time. Keep the tab visible or check back periodically.
- ⚠ Stopping early on fast events. For anything under a few seconds, human reaction time is a meaningful fraction of the measurement.
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Last updated: · by CalculatorPro Tools