Online Stopwatch
Start, stop, lap and reset in one click. Free, no install — runs entirely in your browser.
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Start, stop, lap and reset in one click. Free, no install — runs entirely in your browser.
An online stopwatch is a web-based tool that measures elapsed time with high precision. Unlike a simple timer that counts down, a stopwatch counts up from zero — perfect for measuring how long something takes. TrueTime.zone's stopwatch works directly in your browser with no app or installation required.
Whether you're timing a workout, a cooking task, a presentation, or a race, the stopwatch records time to the millisecond and lets you record lap splits at any point.
performance.now() — a high-resolution timer available in all modern browsers — which is accurate to sub-millisecond precision. The display updates every ~50ms for a smooth visual. For competitive timing, dedicated hardware stopwatches may be more reliable, but for everyday use this is extremely accurate.The first mechanical stopwatch was patented in 1821 by French inventor Nicolas Rieussec, who needed a precise way to time horse races. Early models could measure to the second; by the late 19th century, improvements in escapement mechanisms pushed precision to the tenth of a second. Today, electronic stopwatches — including the one on this page — measure in centiseconds (hundredths of a second), while laboratory-grade atomic timers reach nanosecond precision.
In competitive sports, centisecond accuracy is the difference between a medal and a near-miss. At the 2008 Beijing Olympics, Michael Phelps won the 100m butterfly gold by 0.01 seconds — one centisecond — over Milorad Cavic. FINA touchpads measure to the thousandth of a second; the centisecond display on a web stopwatch is sufficient for training intervals, productivity sessions, and informal timing.
A lap time (also called a split time) records the elapsed time for a single segment of an ongoing activity without stopping the main clock. Runners use splits to assess whether they are pacing correctly — going out too fast in the first kilometre and fading late is a common race-day mistake that split data reveals. TrueTime.zone's stopwatch records both the individual lap time (time for that segment alone) and the total elapsed time at the moment of each lap, giving you full pacing data at a glance.
Beyond sports, lap timing is useful for any repeated task: timing each slide in a presentation rehearsal, measuring how long each step of a recipe takes, or tracking individual calls in a customer service shift.
Timing your work with a stopwatch is one of the most effective ways to combat time blindness — the tendency to underestimate or lose track of how long tasks actually take. Knowledge workers consistently underestimate task duration by 40–60%, a phenomenon known as the planning fallacy (Kahneman & Tversky, 1979). Running a stopwatch during focused work sessions builds an accurate internal clock over time and creates data you can use to plan future work more realistically.
Pair the stopwatch with the Pomodoro Technique: time a 25-minute focused work session, record the lap, then time a 5-minute break. After four laps (two hours of logged work), take a longer break. The visual record of completed sessions is a motivational tool in itself — it makes abstract progress concrete and measurable.