Online Stopwatch

A split time is the duration of one segment on its own — the time elapsed since the previous lap mark — while the cumulative or lap total is the time from the very start up to that mark. If you press lap at 30 seconds and again at 70 seconds, the second split is 40 seconds but the cumulative total reads 70. Splits tell you how each individual segment performed, which reveals whether you sped up or faded; the cumulative figure tells you your overall standing at that point. This stopwatch records both for every lap, so you never have to subtract in your head. It also stars your fastest lap, flags the slowest, and shows the best, average, and worst split across the whole set. Press L while it runs to mark each lap and read both numbers side by side.

A well-built browser stopwatch is accurate to a fraction of a second, which matches or beats most handheld units for everyday timing. The key is the clock source. This tool measures elapsed time with performance.now(), a high-resolution timer that counts from a fixed reference point and is independent of your system's wall clock, so the reading stays correct even if the computer's date or time changes mid-session. The display updates to a hundredth of a second, shown as mm:ss.cc. The realistic limit on accuracy is human reaction time when you tap start and stop — roughly a tenth to two tenths of a second — not the timer itself, so the same caveat applies to a physical stopwatch. For official sports records you still need electronic gate timing, but for training, cooking, study sessions, and rehearsals this is plenty precise. Press Space to start and time anything instantly.

Use the multi-timer panel, which lets you create and run several independent named timers at once instead of being limited to a single clock. Each one can be set as its own count-up stopwatch or its own countdown, and they all tick simultaneously without interfering with each other. This is built for situations where one timer is never enough: cooking different dishes that finish at different times, managing parallel workout intervals, or tracking separate tasks side by side. Because everything runs locally in your browser, adding more timers does not slow anything down or require a sign-up, and each timer keeps its own label so you can tell at a glance which is which. Switch to the multi-timer view, name each timer, set its duration or leave it counting up, and start them whenever you need.

The 25-minute preset is there for the Pomodoro technique, a focus method that breaks work into fixed 25-minute blocks of concentration followed by a short break. Working against a visible deadline tends to reduce procrastination and makes long tasks feel more manageable, which is why a 25-minute countdown has become a popular study and productivity habit. In countdown mode you can tap that preset in one click, or choose 1, 5, 10, 15, 30, or 60 minutes instead, or type any custom duration in hours, minutes, and seconds. A progress bar shows how much time has passed and how much is left, the digits shift to orange and then red as the end nears, and a three-tone beep signals zero so you can step away from the screen. Open countdown mode, tap 25 minutes, and start your first focus block.

Use the split calculator, which works backwards from a goal instead of timing you live. Enter the finish time you are aiming for, the total distance in kilometres or miles, and how many splits you want, and it returns the pace per unit you must hold plus an even split schedule for each segment. For example, a runner targeting a 25-minute 5K can see the required per-kilometre pace and the cumulative time they should hit at each marker. This turns a vague goal into concrete checkpoints you can chase, and it pairs naturally with the live stopwatch: calculate your target splits first, then switch to stopwatch mode and press L at each marker to compare your actual splits against the plan. Enter your goal time and distance in the split calculator to get your pacing targets in seconds.