A few classic workouts
- Tabata: 8 × (20 s all-out effort, 10 s rest), i.e. 4 minutes.
- 30/30 running: 30 s fast (about 100% of maximal aerobic speed), 30 s jogging, in sets of 8 to 12.
- HIIT: 40 s of exercise, 20 s of recovery, going through several exercises.
Does it work with the screen off?
Browsers often suspend background pages. The tool therefore asks to keep the screen on during the workout (where supported); the time stays accurate even after a pause in display, because it is computed from the clock.
Warm up before intense sessions and adapt the intensity to your level.
How to use it
- Pick a preset (Tabata, HIIT, 30/30, core 45/15, boxing 3 min / 1 min, long intervals 4 × 4 min…) or start from scratch.
- Set the durations: work time, rest time, repetitions per set, number of sets and rest between sets. The total duration updates instantly.
- Start the session: the countdown fills the screen, with one colour per phase, readable from several metres away. Three beeps announce each change and a voice can call the next phase.
- Pause at any time; the clock resumes exactly where it stopped.
- Print the session to pin it up in a gym or hand it to a group.
Working out a session's length
Example: 3 sets of 8 repetitions of 40 s work and 20 s rest, with 2 minutes between sets. Each set lasts 8 × 60 s = 8 minutes; three sets make 24 minutes, plus 2 × 2 minutes of rest, i.e. 28 minutes. Add a 10-minute warm-up and a 5-minute cool-down: the full session fits in 45 minutes.
Session ideas by goal
- Beginners: 6 × (30 s moderate effort, 60 s rest). The 1:2 ratio gives time to recover.
- Running, MAS work: 2 sets of 10 × 30/30, 3 minutes between sets. The fast 30 seconds are run at about 100% of MAS (see the pace calculator).
- Circuit training: 40 s of exercise, 20 s to change station, 6–8 different exercises, 2–3 rounds.
- Tabata: 8 × (20 s / 10 s). Only 4 minutes, but at maximal intensity: for people who are already trained.
- Core: 5 × (45 s plank, 15 s rest).
Tips and precautions
- Keep the screen on and the sound up; on a phone, turn off battery saver during the session.
- Quality beats quantity: if you can no longer hold the intensity, stop the set rather than finish it with poor form.
- Two or three hard sessions a week are enough; leave at least 48 hours between very hard ones.
- If you have a heart condition or are returning after a long break, ask a doctor first.
Guide written and checked by Erwan Hautot · updated 5 November 2026.