Interval Timer
Run work and rest rounds from your browser. Start from a Tabata, HIIT, EMOM, boxing or circuit preset, or set the prep, work, rest and round count yourself.
Ready
Pick a preset or set your rounds
00:20
—
Total 04:00
iPhone & Apple Watch · Free
Track it in Workout Timer.
The same interval structure the Workout Timer app runs on iPhone and Apple Watch.
How the interval timer works
Pick a preset or set the four fields yourself: a prep countdown before the first round, the work interval, the rest between rounds, and how many rounds to run. Prep and rest can both be zero — an EMOM has no rest at all, so the timer chains one work interval straight into the next.
The session ends on the final work interval rather than on a trailing rest, which is how Tabata, boxing and CrossFit clocks all count. Eight Tabata rounds are therefore 10 seconds of prep plus eight 20-second work intervals and seven 10-second rests — four minutes exactly.
Remaining time is derived from timestamps rather than counted ticks, so a backgrounded tab that stops firing timers still shows the correct number the moment you switch back to it.
session length = prep + (work × rounds) + (rest × (rounds − 1)) This is a timer, not training advice. Pick intervals suited to your own fitness and check with a qualified professional before starting a new training routine.
Tabata et al., Medicine & Science in Sports & Exercise (1996) — the 20/10 × 8 protocol ↗
Interval timer FAQ
What is the Tabata timer setting?
Twenty seconds of work followed by ten seconds of rest, repeated for eight rounds — four minutes in total. That is the protocol from Izumi Tabata's 1996 study, and it is the Tabata preset here.
What does EMOM mean?
Every Minute On the Minute: you start a new round at the top of each minute and rest with whatever time is left after finishing the work. The EMOM preset is 60 seconds of work with no rest, so rounds chain straight into each other.
How long is a boxing round?
Three minutes of work with a one-minute rest between rounds, which is the boxing preset. Twelve rounds is the championship distance; amateur bouts are usually three rounds.
Can I set it up for HIIT?
Yes. The HIIT preset runs 30 seconds of work against 15 seconds of rest for 10 rounds, and every field stays editable if your intervals differ.
Why does the timer finish on work instead of rest?
Because resting after the last round serves no purpose. A round timer counts the rest between rounds only, so the session stops the moment the final work interval ends.
Does it keep time if I switch tabs?
Yes. Remaining time is calculated from timestamps and recalculated when the page becomes visible again, so a backgrounded tab does not drift.
Can I use it without a prep countdown?
Yes. Set prep to zero and the timer opens directly on the first work interval.
Does the timer make a sound?
Optionally. When you enable sound, the browser generates a short tone at each phase change using the Web Audio API. It is off by default.
Are my settings saved?
No. The timer runs entirely in your browser — no account, no network calls, and nothing stored between visits.