Precise online stopwatch with lap timer and millisecond accuracy. Track splits for running, swimming, or any timed activity.
| Protocol | Work | Rest | Rounds | Total Time |
|---|---|---|---|---|
| Tabata | 20 sec | 10 sec | 8 | 4 min |
| HIIT Classic | 30 sec | 30 sec | 10 | 10 min |
| EMOM | Start each min | Remaining | 10–20 | 10–20 min |
| Sprint Intervals | 15 sec | 45 sec | 10 | 10 min |
| Boxing Rounds | 3 min | 1 min | 12 | 48 min |
| Device | Accuracy | Cost | Best For |
|---|---|---|---|
| This Stopwatch | 1–2ms | Free | Workouts, cooking, general timing |
| Phone App | 5–10ms | Free | Casual timing |
| Digital Stopwatch | 1ms | $15–$50 | Sports training |
| Professional Timing | 0.001ms | $500+ | Olympic / competitive sports |
This stopwatch uses requestAnimationFrame with performance.now() for the highest accuracy available in a browser — typically within 1–2 milliseconds, which exceeds the precision of most phone apps and is sufficient for sports training.
Yes. The stopwatch uses system timestamps (performance.now()) rather than interval-based counting, so it remains perfectly accurate even when the tab is in the background. The display updates when you return.
The Lap button records the time for the current segment while the stopwatch continues running. It shows both the individual lap time and cumulative total time — useful for tracking intervals in running, swimming, or any repetitive activity.
Absolutely! Use the Lap button at the end of each work/rest period. The lap table shows individual segment times and cumulative totals, making it perfect for tracking Tabata, HIIT, sprint intervals, or swimming laps.
For most purposes, yes. Browser stopwatches using performance.now() achieve 1–2ms accuracy, matching most consumer digital stopwatches. Only professional timing systems (Olympic-grade) are more precise at sub-millisecond levels.
Professional-grade stopwatch tool designed for accuracy and privacy. Calcora provides expert-built utilities entirely free of charge with zero data collection.
All calculations happen instantly and locally within your browser, ensuring your data remains absolutely private.
No. Calcora tools run 100% client-side. No data is uploaded or stored on any external server.
Yes, all tools on Calcora are completely free to use without any account or subscription.