Stopwatch
Precise stopwatch with lap times and history
How to use Stopwatch
Precise online stopwatch with lap times and history. Start, pause and reset. Works on mobile. Free online stopwatch tool.
What is a stopwatch used for?
A stopwatch measures elapsed time with precision. In competitive contexts, milliseconds matter. In everyday use, it brings discipline and objectivity to any timed activity.
- Sports and fitness: Time running intervals, swim laps, cycling segments, or rest periods between sets. Lap recording allows comparison across efforts within the same session.
- Cooking: Time boiling eggs, pasta cooking, bread proofing, or any recipe step that requires precise timing — more reliable than estimating.
- Presentations and speeches: Practice a talk within a time limit. Record laps for each section to ensure the timing distribution matches your intent.
- Productivity: Time-track work sessions with the Pomodoro technique, measure how long tasks actually take (vs estimates), or run a time audit of your day.
- Science experiments: Time chemical reactions, measure velocity over a known distance, or record experiment durations for data logging.
Lap vs split timing: A lap time records the duration of the most recent interval (time since last lap press). A split time records total elapsed time at each lap press. Lap times show each segment's duration; split times show cumulative progress. Most race timing uses splits; interval training uses laps.
Frequently Asked Questions
What is the difference between a stopwatch and a timer?
A stopwatch counts up from zero — you start it when the event begins and stop it when it ends. A timer counts down from a preset value to zero — you set the duration and it alerts when done. Both measure time intervals, but the mental model differs: stopwatches measure unknown durations; timers enforce known durations.
How accurate is a browser stopwatch?
JavaScript's Date.now() has millisecond resolution but browser timer callbacks can drift by 1-15ms due to event loop scheduling. For everyday timing, this is imperceptible. For scientific measurements or competition timing requiring sub-millisecond accuracy, dedicated hardware is more appropriate.
What is a flying start vs standing start?
A standing start begins timing when the athlete starts moving from rest. A flying start begins timing when the athlete crosses the start line already at full speed. Track sprints use standing starts; speed trap measurements use flying starts. The difference matters significantly for performance comparison.
Can I time multiple things simultaneously?
This stopwatch tracks one elapsed time with multiple laps. For timing multiple simultaneous events (like multiple athletes), you need multiple stopwatch instances or a multi-lane timing system. Open multiple browser tabs with this tool for a simple multi-timer solution.
What is the world record for the 100m sprint and how is it measured?
Usain Bolt's 9.58 seconds (Berlin, 2009) is measured by fully automated timing (FAT) — photo-finish cameras and pressure-sensitive starting blocks accurate to 0.001 seconds. Manual stopwatch timing by officials was standard until the 1970s and was accurate to approximately 0.1 seconds.
Browser stopwatch vs dedicated app vs hardware stopwatch
A hardware stopwatch (Casio, sports watch) is reliable and portable — no battery drain concerns, works offline, survives outdoor conditions. A dedicated phone app (Interval Timer, Nike Run Club) offers advanced features — GPS tracking, automatic lap detection, training plans. A browser-based stopwatch is instantly accessible on any device without installing anything — ideal for occasional use at a desk. For serious sport training, a dedicated app or hardware watch is more appropriate.