Online stopwatch with laps + countdown timer in your browser
This tool provides two essential time measurement functions: a Stopwatch for measuring elapsed time with lap recording, and a Countdown Timer that counts down from a set duration and alerts you when time is up. Both work entirely in your browser — no app download, no login required.
The Stopwatch is precise to 1/10th of a second and supports unlimited laps. The Countdown Timer supports hours, minutes, and seconds and shows a visual alert when the countdown completes.
The Stopwatch uses JavaScript's performance.now() or Date.now() for millisecond-level timing. The display is updated every 100ms. Lap times are calculated as the difference between consecutive lap presses. The Countdown Timer calculates remaining time by subtracting elapsed time from the total input duration, updated every second using setInterval.
Pomodoro technique: 25 minutes work, 5 minutes break. Boiling eggs: 7–10 minutes. Pasta cooking: 8–12 minutes. HIIT workout intervals: 20–45 seconds on, 10–20 seconds rest. Tea steeping: 2–5 minutes. Medicine reminder: 4–8 hours. Sprint planning: typically 1–2 hours. Presentation practice: 10–20 minutes.
Athletes timing their sprint, swim, or run performance. Cooks timing food preparation steps. Students using Pomodoro technique for study sessions. Teachers timing class activities and tests. Gym-goers timing rest periods between sets. Speakers rehearsing presentations within time limits. Event organizers managing agenda segments. Developers timing code execution for performance testing.
For sports timing, keep the browser tab active — background tab throttling may affect accuracy. Use the lap button to record split times without stopping the stopwatch. For the countdown timer, enter exact hours, minutes, and seconds — it supports 0-99 hours. The timer plays no sound by default (browser restrictions), but shows a visible red flashing alert when complete.
A stopwatch measures elapsed time — how much time has passed since starting. A countdown timer measures remaining time — how much time is left until zero. Both are forms of interval timing. Professional timing systems (used in Olympics) measure to 1/1000 second (1 millisecond). This browser-based tool is accurate to approximately 100ms, suitable for everyday use but not official sports competitions.
Click Start to begin timing. Click Lap to record a split time without stopping. Click Start again (it becomes Pause) to pause the stopwatch. Click Reset to clear and start over. Lap times appear in the list below, showing both the lap time and cumulative total time.
Switch to the "Countdown Timer" tab. Enter hours, minutes, and seconds in the input fields. Click Start to begin the countdown. The remaining time displays in large digits. When it reaches zero, a green "Time's Up!" message appears. Click Reset to clear and start again.
Browser background tabs may experience timer throttling — for precision timing, keep the tab active. No audio alert is played (browser autoplay restrictions). This tool does not use device system time for elapsed counting — if the browser sleeps (mobile screen lock), the timer may be inaccurate. Not suitable for official sports or scientific timing requiring sub-100ms precision.