About This Tool
Measure elapsed time down to the hundredth of a second with this free online Stopwatch. Press Start to begin timing, record lap splits as you go, and review your results in a detailed table that highlights the fastest and slowest laps automatically. All times are displayed in HH:MM:SS.ms format for precision, and you can copy individual times or the entire lap history to your clipboard with a single tap. This stopwatch is built for accuracy and simplicity. It tracks time using high-precision device timing, so the display stays precise even if you switch tabs or minimize the window. The lap feature records both individual lap durations and cumulative split times, making it useful for running, swimming, cycling, cooking, scientific experiments, and any activity where segment timing matters. Summary boxes above the lap table display your total number of laps, the fastest segment highlighted in green, and the slowest segment highlighted in red, giving you a quick performance overview without scanning every row. No account, installation, or permissions required. Open the page, hit Start, and you are timing. Your data stays completely private with no tracking, no storage, and no transmission. When you are finished, copy your laps to paste into a spreadsheet, training log, or lab notebook. The tab-separated export format works with Excel, Google Sheets, and most data analysis tools, so your timing data is always portable and ready for deeper review.
How to Use the Stopwatch
Using the stopwatch is simple:
- Press Start to begin timing from zero.
- Press Lap to record a split. Each lap captures the time since the previous lap (or since start) and the cumulative time from the beginning.
- Press Stop to pause the stopwatch. The elapsed time freezes and you can resume or reset.
- Press Resume to continue from where you stopped, or Reset to clear everything and start fresh.
Laps appear in a scrollable table sorted newest first. When you have recorded two or more laps, the fastest lap is highlighted in green and the slowest in red, giving you instant feedback on your performance. Use the Copy buttons to export the current time or the full lap table to your clipboard.
Lap Times vs. Split Times
Understanding the difference between lap times and split times is essential for performance analysis:
- Lap time (also called segment time) measures the duration of a single segment. It tells you how long that particular lap took.
- Split time (also called cumulative time) measures the total elapsed time from the very start to the end of that lap.
For example, if a runner completes three laps of a track in 1:30, 1:25, and 1:35, the split times would be 1:30, 2:55, and 4:30. The split times always increase, while lap times can vary. Comparing lap times reveals pacing consistency: a runner who starts fast and slows down has a "positive split," while one who speeds up has a "negative split." Most coaches recommend even splits for optimal race performance.
This stopwatch records both values automatically so you can analyze pacing, identify your strongest segments, and spot areas for improvement without manual subtraction.
Practical Applications
A precision stopwatch has uses far beyond athletics:
- Running and track: Time individual laps, record personal bests, and compare training sessions over weeks of data.
- Swimming: Capture split times per length or per stroke cycle to fine-tune technique.
- Cooking: Track how long a sauce reduces, how quickly oil reaches temperature, or how long bread proofs.
- Science and education: Time chemical processes, pendulum swings, or student response intervals for experiments.
- Gaming and speedruns: Log segment times to track progress toward record runs.
- Public speaking: Rehearse presentations and record section durations to ensure you stay within your allotted time.
- Manufacturing and quality control: Time assembly steps to identify bottlenecks and improve throughput.
The copy-to-clipboard feature makes it easy to transfer your recorded times into a spreadsheet or document for further analysis.
Reading Your Results
After recording several laps, the results table and summary boxes give you a complete picture of your timing data:
- Total Laps shows how many segments you have recorded.
- Fastest Lap displays the shortest individual lap time, highlighted in green in the table. This is your peak performance segment.
- Slowest Lap displays the longest lap time, highlighted in red. This shows where you lost the most time.
The table lists each lap with its number, individual duration, and cumulative split time. Laps are shown newest first so the most recent result is always at the top. Comparing your fastest and slowest laps reveals your consistency. A narrow gap between the two means steady pacing, while a wide gap suggests you could benefit from more even effort distribution.
For multi-session tracking, copy each session's laps and paste them into a spreadsheet. Over time, you will build a dataset that reveals trends in performance, recovery, and improvement.
Tips for Accurate Timing
Maximize the accuracy of your stopwatch results with these practices:
- Use a consistent trigger: Always start and stop on the same cue (a sound, a movement, crossing a line) to reduce response-time variability.
- Minimize response delay: Position your finger over the Lap or Stop button before the event occurs so your response time is as short as possible.
- Record multiple trials: For scientific measurements, repeat the timing at least three times and use the average to reduce random error.
- Keep the tab active: While the stopwatch remains accurate in background tabs, the display updates more smoothly when the tab is visible.
- Copy results immediately: After finishing a timed session, copy your laps before resetting so you have a permanent record.
Human response time averages around 200-250 milliseconds. For timing events where that margin matters, consider using the lap function at fixed intervals and comparing segments rather than relying on a single start/stop measurement.
Frequently Asked Questions
How precise is this online stopwatch?
The stopwatch tracks time to the hundredth of a second (10-millisecond resolution). It uses high-precision device timing for reference, which is accurate under normal conditions. The primary source of imprecision is human response time when pressing Start, Stop, or Lap, not the timer itself.
Can I record laps while the stopwatch is running?
Yes. Press the Lap button at any time during an active session. Each press records both the individual lap duration (time since the previous lap or start) and the cumulative split time. The stopwatch continues running without interruption while laps are recorded.
What is the difference between lap time and split time?
Lap time is the duration of a single segment (from the previous lap marker to the current one). Split time is the total elapsed time from the initial start to the current lap marker. Split times always increase, while lap times vary based on performance per segment.
How do I export my lap data?
Use the "Copy All Laps" button to copy the full lap table (lap number, lap time, and split time) to your clipboard in a tab-separated format. You can paste this directly into a spreadsheet application like Excel or Google Sheets for further analysis, charting, or long-term record keeping.
Does the stopwatch keep running if I switch tabs?
Yes. The stopwatch anchors its calculations to an absolute time reference, so switching tabs, minimizing the window, or even locking your screen does not affect the elapsed time. When you return to the tab, the display updates immediately to show the correct value.
What do the green and red highlights in the lap table mean?
Green highlights the fastest lap (shortest individual lap time), and red highlights the slowest lap (longest individual lap time). These highlights appear once you have recorded two or more laps, giving you quick visual feedback on your best and weakest segments.