Stopwatch (Duration Calculator)
Drop in durations in any common format ('1:23:45', '90:00', '1h 30m', '2.5h', '90s') and format, add, or subtract them. Output is given in HH:MM:SS, total seconds, and a human-readable form like '1h 30m 45s'. Heads up: this is a calculator, not a real-time stopwatch — for an interactive timer you can start and stop, use your phone's clock app. This tool is for the 'how long total did I spend on X' or 'what's 1h 25m plus 47 minutes' kind of question. Runs entirely in your browser.
Privacy
Runs entirely in your browser — nothing is sent to any server.
Cost
Free. No sign-up, no watermark.
Type
Calculator
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Frequently asked
Is Stopwatch (Duration Calculator) free to use?
Yes. Stopwatch (Duration Calculator) is completely free with no sign-up, no watermark, and no usage limits. Toolsly does not charge for any of its tools.
Do my files and data stay private?
Yes — Stopwatch (Duration Calculator) runs entirely in your browser using your device's CPU. Files and text are never uploaded to our servers, so your data stays private.
How does Stopwatch (Duration Calculator) work?
Open Stopwatch (Duration Calculator), paste or fill in the input fields, and the result updates instantly. Everything runs in your browser — no upload, no waiting.
Which browsers does Stopwatch (Duration Calculator) support?
Any modern browser works — Chrome, Firefox, Safari, and Edge on desktop and mobile. Stopwatch (Duration Calculator) uses standard web APIs and does not require any plugin, extension, or sign-up.