Online stopwatch
Time any activity with precision — start, pause, reset, and record unlimited lap splits. The fastest and slowest laps are highlighted automatically.
What is the Online Stopwatch?
A precise stopwatch for workouts, races, cooking, and any task you want to time. Measures down to hundredths of a second. Tap Lap while running to record splits — the fastest and slowest laps are highlighted so you can see your consistency at a glance. The stopwatch uses a high-resolution timer that stays accurate even when the browser tab is in the background.
Keyboard shortcuts
Space to start or stop, L to record a lap, Esc to reset.
Common Uses
- Athletic training and lap timing: Record split times for running laps, swim lengths, or cycling intervals to track performance improvements over time.
- Presentation rehearsal: Time rehearsals for conference talks, pitches, or classroom presentations to stay within the allotted slot.
- Cooking and recipe timing: Time sauté, blanching, or resting steps that require precision without reaching for a separate kitchen timer.
- Reaction time measurement: Measure personal reaction time or run informal experiments comparing reaction before and after stimulants like caffeine.
- Board game turn timing: Enforce equal thinking time per player in strategy games to keep the session moving and prevent analysis paralysis.
- Work rate benchmarking: Measure how long a task actually takes (versus estimated) to improve planning and identify bottlenecks in workflows.
- Scientific and lab experiments: Time reactions, incubations, or centrifuge runs in educational or home lab settings without dedicated lab equipment.
FAQ
How accurate is this stopwatch?
The display updates every 50 milliseconds and uses the browser's high-resolution performance timer under the hood, so times are accurate to within a few milliseconds. Hundredths are shown for fine-grained splits.
What do the highlighted laps mean?
Once you've recorded at least two laps, the fastest lap is shown in green and the slowest in red. This makes it easy to spot your best and worst splits at a glance.
Can I use this for race timing?
Yes, for casual timing. It's not certified for competitive events — a dedicated sports stopwatch is more precise — but it's great for training runs, intervals, and everyday timing tasks.
Does the stopwatch store my timing data?
No. Stopwatch times and lap splits exist only in the browser tab's memory. Nothing is saved to a server or your device's storage.
How accurate is the browser stopwatch?
The stopwatch uses the browser's high-resolution performance timer, which typically has sub-millisecond accuracy. It is suitable for timing sports, cooking, experiments, and most practical activities.
By the Numbers
- NIST's most precise atomic clocks lose less than 1 second in 300 million years, based on cesium-133 hyperfine transitions
- Olympic athletic events are timed to 1/1,000th of a second using precision photofinish technology (World Athletics)
- The average human visual reaction time is ~250 milliseconds (¼ second) — a measurable personal performance baseline
- Light travels approximately 30 cm (1 foot) in 1 nanosecond — the clock speed at which modern computer chips operate