20 Second Timer
A ready-to-go 00:20 countdown -- press Start, or set a different duration below if you need one.
Keyboard: Space start/pause, R reset, Esc stop alarm.
What a 20 second timer is used for
- the length the CDC recommends for washing your hands with soap
- roughly two rounds of "Happy Birthday" sung through, the informal handwashing timer
- a quick warm-up set at the start of a workout
- a short breathing-reset pause between reps
- a brief transition buffer between two quick tasks
Why 20 seconds
Twenty seconds has one very specific, very well-known citation: it's the minimum hand-washing duration recommended by the U.S. Centers for Disease Control and Prevention and the World Health Organization, and "sing Happy Birthday twice" became the informal public-health shorthand for timing it without a clock in the room.
20 seconds = 0.33 minutes = 1/180 hour
How it stays accurate
Like every timer on this site, this one never counts down by subtracting one second at a time -- it records the exact target end timestamp the moment you press Start, then recomputes the time left from that fixed target on every screen update. Switching tabs, minimizing the window, or letting the browser throttle a background tab doesn't cost any accuracy, because the next update still does the subtraction fresh rather than trying to catch up on missed ticks. The alarm itself is synthesized with the Web Audio API -- no audio file, nothing an ad blocker could interfere with -- and repeats until you stop it with the Escape key, the Stop alarm button, or by starting a new countdown.
Frequently Asked Questions
What is a 20 second timer good for?
A few common uses: the length the CDC recommends for washing your hands with soap; roughly two rounds of "Happy Birthday" sung through, the informal handwashing timer; a quick warm-up set at the start of a workout.
How long is 20 seconds in other units?
20 seconds = 0.33 minutes = 1/180 hour.
Does this 20 second timer stay accurate if I switch tabs?
Yes -- it stores the exact moment the countdown should end and recomputes the time left from that fixed target on every update, rather than counting ticks, so a background tab that gets throttled for a while doesn't cost any accuracy.
Why is 20 seconds a notable duration?
Twenty seconds has one very specific, very well-known citation: it's the minimum hand-washing duration recommended by the U.S. Centers for Disease Control and Prevention and the World Health Organization, and "sing Happy Birthday twice" became the informal public-health shorthand for timing it without a clock in the room.