Number base converter
Convert integers exactly between bases 2–36, including negative and very large values, with common base results shown together.
Stopwatch and countdown timer
Measure elapsed time with laps or set a countdown, pause and resume, and export lap records to CSV.
Keep this page open. Background tabs may delay the sound; navigating away clears the timer and laps.
About this tool
Measure elapsed time with laps or set a countdown, pause and resume, and export lap records to CSV.
How to use
Choose stopwatch or countdown. Start, pause and resume with the main button. In stopwatch mode, record laps and download them with split and total times. In countdown mode, set hours, minutes and seconds, with an optional finishing sound.
The display is calculated from elapsed time, not interval tick counts. Keep the page open: background tabs and suspended devices can delay sound or updates. Leaving the page clears records. Countdown supports up to 99 hours, 59 minutes and 59 seconds; lap limit: 500.
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