Stopwatch

A precise online stopwatch with laps and splits

The Stopwatch measures elapsed time to the hundredth of a second, right in your browser. Start, stop and resume as often as you like, record lap times with one tap or key, and see each lap’s time, the running total (split), and whether it was faster or slower than the lap before. The fastest and slowest laps are highlighted automatically.

It is built for real use: big digits you can read from a distance, a full-screen mode, keyboard shortcuts, CSV export for spreadsheets, and it keeps counting even if you reload or close and reopen the page.

How to use the Stopwatch

1. Press Start (or the Space bar) to begin timing.
2. Press Lap (or L) each time a lap, rep or segment finishes. The current lap time shows under the main display.
3. Press Stop (or Space) to pause, then Resume to continue from the same time.
4. Review the lap table: lap time, total split and the change versus the previous lap. Fastest and slowest are marked.
5. Use Download CSV or Copy laps to save your results, and Reset (or R) to start over.

Stopwatch features

Lap time vs split time

A lap time is the duration of one segment on its own — for example the 400 m you just ran. A split time (shown as “Total”) is the cumulative time from the start up to the end of that lap. If you run laps of 92.4 s and 95.1 s, your splits are 1:32.40 and 3:07.50.

The “vs previous” column compares each lap with the one before it. A minus sign (in green) means the lap was quicker; a plus sign (in red) means it was slower. Coaches use this to spot pacing problems: steady or negative splits — where later laps are as fast or faster — usually mean a well-paced effort.

How accurate is an online stopwatch?

This stopwatch does not count ticks. It stores the exact moment you pressed Start and, whenever the screen refreshes, subtracts that from the current time. That means it stays correct even when your browser slows down background tabs to save battery, or when your phone briefly sleeps — the time is simply recalculated when you look again.

The display updates with your screen’s refresh rate, so the hundredths are as precise as the clock allows. In practice the biggest source of error is human: reaction time to press a button is typically around 0.2 seconds, and it applies at both start and stop. For races that need better accuracy, sports use automatic timing systems.

Ideas for using the stopwatch

• Running, swimming and cycling: record each lap and compare pace — the Pace Calculator converts times into pace per km or mile.
• Workouts: time sets, rest periods and holds such as planks.
• Speeches and presentations: rehearse and see how long each section takes.
• Science experiments and classes: measure reaction times or how long a process takes, then export the laps to a spreadsheet.
• Need to count down instead? Use the Countdown Timer. To add up several recorded durations, try the Time Duration Calculator.