A stopwatch measures elapsed time with start, stop, and reset functions. Digital stopwatches measure to 1/100th of a second (10ms). Lap times measure split segments. Used in sports, cooking, science experiments, and productivity.
Tip: For accurate sports timing, the reaction time of the starter is often as significant as timer precision. Human reaction time averages 150–300ms — far greater than the ±10ms precision of most stopwatches.
- 1Records timestamp when started
- 2Elapsed = current time − start time
- 3Lap time = current time − last lap timestamp
- 4Accuracy limited by browser/OS timer resolution (~1–4ms)
| Tool | Accuracy | Best use |
|---|---|---|
| Phone stopwatch | ~10ms | Most sports timing |
| Hardware stopwatch | ~1ms | Precision athletics |
| Quartz crystal oscillator | ~0.0001ms | Scientific timing |
| Atomic clock | <0.000001ms | GPS, fundamental science |
| Browser JavaScript | ~4ms (varies) | Web apps |
Fun Fact
The world's most accurate clock — an optical lattice clock — loses or gains less than 1 second in 30 billion years. For context, the universe is only 13.8 billion years old. These clocks are so accurate they can measure the difference in the flow of time between heights that differ by just 1 centimeter.
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