Online Stopwatch
Space to start and pause, L for laps. Stays accurate even in a background tab.
Shortcuts: Space start/pause · L lap · R reset
No laps yet
| Lap | Split | Total |
|---|
Lap, split, and total time — what the stopwatch actually records
A stopwatch looks trivial until you start taking laps, and then the numbers need care. This tool keeps three quantities straight: the total elapsed time since you pressed start, the split for each lap (how long that one segment took), and the running lap count. Understanding the difference is what makes the recorded times useful afterwards.
How to use it
- Press Start (or the Space bar) to begin. The display counts up in minutes, seconds, and hundredths.
- Press Lap (or L) each time you complete a segment — a track lap, a workout set, a stage of a task.
- Press Reset (or R) to clear everything and start fresh. Copy the lap table first if you want to keep it.
Split versus total
Each row stores the total time at the moment you tapped Lap. The split for a lap is simply the difference between its total and the previous lap's total: split(n) = total(n) − total(n−1). The timing is based on the browser's high-resolution monotonic clock, so it does not drift with the system clock and stays accurate even if the visual display is briefly throttled.
Reading a lap table
| Lap | Split (this lap) | Total (cumulative) |
|---|---|---|
| 1 | 1:02.50 | 1:02.50 |
| 2 | 1:05.80 | 2:08.30 |
| 3 | 1:07.10 | 3:15.40 |
| 4 | 1:04.70 | 4:20.10 |
Where hundredth-second timing helps
The lap and split breakdown is what turns a raw timer into a training or work log. Runners compare each 400 m split to spot where pace fades; swimmers check whether the back half of a set slows; presenters rehearse to a target and see which section runs long; cooks and lab users mark stages of a process without resetting the clock. Because every lap keeps both its own split and the cumulative total, you can copy the whole table afterwards and analyse the session at once. The keyboard shortcuts — Space to start or pause, L to lap, R to reset — keep your hands free during an activity, and the monotonic clock means a throttled or backgrounded tab will not corrupt the elapsed count.
Common mistakes and tips
- Confusing split with total: a reading of "2:08" is usually cumulative time, not a single lap that took over two minutes. Read the split column for per-segment pace.
- Expecting an alarm: a stopwatch counts up with no target. If you need it to stop at a set time, that is a countdown timer instead.
- Losing data on reset: reset wipes the laps. Use Copy results first to paste them into your notes.
- Hundredths, not thousandths: the display resolves to 0.01 s, which is plenty for human timing; it is not a photo-finish instrument.
Nothing is uploaded — the timer runs entirely in your browser.
Sources & further reading
Frequently asked questions
Is the stopwatch accurate when the tab is in the background or the device is asleep?
Yes. Instead of adding up ticks, this online stopwatch records the moment you press start and, on every frame, recomputes elapsed time as the difference from the system clock. So even if the browser throttles a background tab or the screen sleeps, the time is correct the instant you return — no drift piling up.
What's the difference between a lap (split) and the total time?
The total is the full time since you pressed start. A lap — also called a split — is the time for that segment alone: the gap between one lap press and the previous one. Press L or the Lap button and the stopwatch records both, so you see each interval and the running total side by side. With two or more laps, the fastest is highlighted in green and the slowest in red.
Do my times survive a page refresh or closing the browser?
Yes. The running state and every lap are saved in your browser's localStorage under the stopwatch: key, and nothing is sent to a server. Refresh the page or reopen it later and a stopwatch that was running keeps counting from the right moment, with all laps intact. Reset clears them.
What are the keyboard shortcuts?
Space starts and pauses, L records a lap, and R resets. The shortcuts read physical key positions, so they work the same on any keyboard layout or input method, and they're ignored while you're typing in a field — so they never get in the way.
How do I paste my lap times into Excel or Google Sheets?
Press Copy results and the laps are copied as tab-separated text — lap number, split and total per line. Paste into Excel, Google Sheets or Numbers and each value lands in its own cell automatically. If the browser blocks the clipboard, the results appear on screen so you can select and copy them by hand.