Online Stopwatch
A precise online stopwatch with lap times, keyboard shortcuts and millisecond accuracy. No download or sign-up needed.
00:00.00
Stopwatch readySpace starts and stops · L records a lap · R resets
About Stopwatch
A stopwatch accurate to the millisecond, driven by the browser's high-resolution clock rather than a counter, so it stays exact even if the tab is backgrounded. Record laps, review the fastest and slowest, and control everything from the keyboard.
How to use it
- Press Start, or hit Space.
- Press Lap (L) to record a split without stopping.
- Press Reset (R) to clear and start again.
Frequently asked questions
Does it keep time if I switch tabs?
Yes. Elapsed time is calculated from timestamps rather than counted frame by frame, so background throttling affects only how often the display refreshes, never the recorded time.
What are the keyboard shortcuts?
Space starts and stops, L records a lap, and R resets.
How accurate is it?
It uses performance.now(), which is accurate to well under a millisecond. In practice your reaction time is thousands of times larger than any error here.
Trending guides
In-depth reads that go beyond the calculator.
- Trending6 min read
SIP Calculator guide
A Systematic Investment Plan is a standing instruction to put a fixed amount into a mutual fund on the same date each month. That is the whole idea. It is not a product you buy, not an asset class, and not a scheme with a guaranteed rate — it is a schedule. The returns come from whatever the underlying fund holds.
- 3 min read
BMI Calculator guide
Body Mass Index is weight in kilograms divided by height in metres squared. That is the whole calculation. It was devised in the 1830s by the Belgian statistician Adolphe Quetelet, who was explicitly describing populations rather than assessing individuals — a distinction that matters enormously and gets lost constantly.
- 3 min read
Percentage Calculator guide
Almost every percentage problem is one of four shapes. Knowing which one you are looking at is most of the work, because each has a different formula and mixing them up is where the wrong answers come from.