Interval timer
Get ready
0 of 8 rounds done
08:50 left in the whole session
This structure runs 8 minutes 50 seconds end to end, of which 5 minutes 20 seconds is work.
This browser does not offer the Screen Wake Lock API, so the display can still dim or sleep while the timer runs. Set the screen timeout on the device before a talk or a class.
Rounds of work and rest with optional prepare and cool-down phases, and a cue for each.
How a session is built
A session is a lead-in, then a run of rounds, then a cool-down. Each round is a work interval followed by a rest interval, and the rest after the final round is dropped automatically because there is nothing left to recover for. Set prepare or cool-down to zero to leave either one out. The stage always shows which phase you are in and which round you are on — round three of eight, in plain words.
Cues you can follow without looking
Each phase has its own audible cue: a double beep to get ready, a bright two-note rise into work, a single low tone for rest, and a three-note flourish at the end of the session. That matters when your eyes are on the floor or a bar. Every cue is paired with a visible phase change and a written announcement, and the whole set can be muted.
Common structures
Forty seconds of work with twenty seconds of rest across eight rounds is a durable circuit default. Thirty on, thirty off suits strength intervals with a partner. Twenty seconds of work with ten seconds of rest, repeated eight times, is the pattern commonly called Tabata after the Japanese researcher Izumi Tabata, whose 1996 study examined a similar protocol; the name here describes the pattern only.
Timing you can trust mid-session
Every phase boundary is computed from the instant the session started rather than from counted ticks, so round eight begins exactly where the arithmetic says it should, not two seconds late. Switch tabs, lock the phone, come back — the session is where it should be, and a reload resumes it rather than restarting it.
Questions
- Why is there no rest after the last round?
- Because it would be dead time. The session moves straight from the final work interval to the cool-down, or ends there if the cool-down is set to zero.
- Can I share a session with a class?
- Yes. Copy preset link produces a URL such as ?work=40&rest=20&rounds=8&prep=10s&cool=1m — bare numbers are read as seconds — and it opens the same session for anyone who follows it.
- Does the timer keep time if the phone screen locks?
- The clock itself does, because elapsed time is measured against the system clock rather than counted. Audio cues may be suppressed while the screen is locked, so the timer requests a screen wake lock where the browser supports one.
- How many rounds can I set?
- Up to ninety-nine, with work, rest, prepare and cool-down each up to an hour. The page shows the total session length and how much of it is work.
- Is this suitable as medical or training advice?
- No. It is a clock. Choose intervals appropriate to your own fitness, and take advice from a qualified coach or clinician rather than from a timer.