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
Time a practice session or record several laps, then export the split and cumulative times as 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.
Common questions
Will the alarm reliably sound in the background?
A background tab or suspended device can delay updates and sound. Keep the page open; leaving it clears the records. Elapsed time is calculated independently of display ticks.
What is the difference between lap time and total time?
Lap time measures the interval since the previous lap; total time is the cumulative running time. Paused time is excluded. Download the lap CSV before resetting or switching modes, because those actions clear the records. Up to 500 laps are retained.
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