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Stopwatch

Free online stopwatch with start, stop, lap, and reset. Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.

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How to use

1

Start timing

Press Start (or Space) to begin measuring elapsed time.

2

Lap or pause

Use Lap to record a split without stopping, or Stop to pause.

3

Reset

Clear the timer and laps when you are done (R on desktop).

Stopwatch specification

Version 2.0.0 · Runtime tested · Local-first

App status
  • Runtime tested Passed
  • Local-only Verified
  • Server data transfer None
  • App version 2.0.0

Local-first runtime specification · Review policy

Definition
A stopwatch measures elapsed time from a start moment, optionally recording intermediate lap times.
What it does
Elapsed milliseconds from Start, with optional lap list and pause/resume.
Inputs
  • Start / Stop toggle
  • Lap (optional splits)
  • Reset
Outputs
  • Elapsed time as MM:SS.cc
  • Ordered lap list
Rules
elapsed = accumulated + (now − startAt) while running
Assumptions
  • Uses the device Date.now() clock.
  • Paused time is held in accumulated milliseconds.
  • Laps store total elapsed at the moment of Lap.
Units
  • Time: minutes, seconds, centiseconds
Limitations
  • Lap with zero elapsed does nothing.
  • Reset clears elapsed time and all laps.
  • Background tabs may throttle timers; keep the tab open for best continuity.
Example
Start → Lap at 00:12.50 → Stop at 00:45.10 → two laps and paused total
Validation cases
  • Start then Stop → Elapsed freezes; Start resumes
  • Lap while running → New lap row; main clock continues
  • Reset → 00:00.00 and empty laps
Sources
  • Browser Date.now() monotonic wall-clock sampling
App version
2.0.0

About this tool

Details and tips for this tool.

The Stopwatch measures elapsed time with centisecond precision. Start, stop, record laps, and reset—ideal for workouts, labs, cooking steps, or any task where you need to know how long something takes.

Controls sit under a large elapsed readout so you can operate on mobile without scrolling past a chart. Timing never leaves your device.

→ Countdown Timer › → Alarm Clock › → Current Time › → Today's Date ›

Frequently asked questions

Key distinctions behind the tool.

Is the online stopwatch free?

Yes. Start, stop, lap, and reset with no account and no download.

Does it support lap times?

Yes. Press Lap while timing (or L on a keyboard) to record splits without stopping the main clock.

How precise is the display?

The readout shows minutes, seconds, and centiseconds using your device clock.

Are there keyboard shortcuts?

On desktop, Space starts or stops, L records a lap, and R resets.

Is timing sent to a server?

No. Elapsed time and laps stay in your browser.