Interval Timer for HIIT and Tabata

Interval training alternates hard efforts with recovery. An interval timer runs that structure for you and tells you, by sound and color, when each phase starts, so you can concentrate on moving.

A program here is built from these parts, in this order:

1. Warm-up: a get-ready countdown or a full warm-up.
2. Work and Rest, repeated for the number of Rounds.
3. Sets: the whole block of rounds repeated, with an optional longer Rest between sets in place of the last rest of each set.
4. Cool-down: easy movement at the end.

The total time and the work-to-rest split update as you type, and the timeline under the timer shows every phase to scale. Click any block to jump to it.

Tabata is the 20-on, 10-off format named after Japanese researcher Izumi Tabata. In a 1996 study published in *Medicine and Science in Sports and Exercise*, his team had fit young men pedal an exercise bike for 20 seconds at very high intensity (roughly 170% of their VO2max), rest for 10 seconds, and repeat for 7 to 8 rounds, five days a week for six weeks. That short protocol improved both aerobic capacity (VO2max) and anaerobic capacity.

The Tabata preset reproduces the timing: 20 seconds of work, 10 seconds of rest, 8 rounds, which is exactly 4 minutes, after a 10-second get-ready. Most gym classes now apply the format to squats, burpees or kettlebell swings rather than a bike.

Health note: the original protocol was an all-out effort by fit young men in a lab. High-intensity intervals are demanding; warm up first, scale the effort to your fitness, and check with a doctor before starting if you are new to exercise, pregnant, or have a heart, lung or joint condition.

EMOM means "every minute on the minute": at the start of each minute you do a set number of reps, and whatever remains of that minute is your rest. The timer marks each new minute with a tone. Boxing rounds follow the professional standard of 3-minute rounds with 1 minute between them.

All totals above exclude the 10-second get-ready, and the boxing preset skips the pointless final rest.

Sets repeat your block of rounds. Three sets of a Tabata block with a 1-minute rest between them looks like this:

Get ready 0:10
Set 1: (Work 0:20 + Rest 0:10) × 7, Work 0:20, Set rest 1:00
Set 2: (Work 0:20 + Rest 0:10) × 7, Work 0:20, Set rest 1:00
Set 3: (Work 0:20 + Rest 0:10) × 8

The rest between sets *replaces* the last short rest of each set, so you never get a 10-second rest followed by a 60-second one. Set it to 0:00 to keep the normal rest instead. Turn on Skip the final rest to end the moment the last work interval finishes.

Phase changes are calculated from your device clock, so the timer never drifts, and beeps are scheduled up to 90 seconds ahead on the audio clock, which desktop browsers do not throttle in background tabs. Your music app can play alongside it.

Two honest limits: voice cues use your device's speech engine, which needs the page to be active, and phones pause web pages when the screen locks. For a workout on a phone, keep the page open, turn on Keep screen awake, and use Focus mode so you can read the countdown from a distance.