Use the free Interval Timer below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
High-intensity interval training, usually called HIIT, is built on a simple idea: short bursts of hard work, followed by short rests, repeated for several rounds. A twenty-minute HIIT session can feel harder than an hour of steady exercise, because the work periods demand full effort and the rest periods are just long enough to catch your breath before the next burst. The hard part of HIIT is not the exercise itself. It is the timing. Watching a clock while doing burpees is miserable, and guessing the intervals ruins the workout. The Interval Timer solves that by calling the shots for you.
The timer runs a simple cycle: a work period, then a rest period, repeated for as many rounds as you set. The defaults are thirty seconds of work, fifteen seconds of rest, and eight rounds, which gives a six-minute session. You can change all three numbers. Beginners often start with twenty seconds of work and thirty seconds of rest, which keeps the effort manageable. Fitter users go to forty seconds of work and twenty of rest. The timer shows the current phase in large letters, the seconds left, and the round number, and it beeps at every change of phase so you can keep your eyes on your form, not on the screen.
A good HIIT session is built before the timer starts. Pick four to six exercises you know well: squats, push-ups, jumping jacks, mountain climbers, lunges and planks are all solid choices. Arrange them so the same muscles are not worked twice in a row. Write the order on a card where you can see it, because mid-workout is a bad time to decide what comes next. Warm up for three to five minutes first with light movement, and plan a cool-down stretch for the end. The timer handles the timing; you handle the exercises.
During the work periods, effort matters more than speed. The point of HIIT is high intensity, which means you should be breathing hard and unable to hold a conversation by the end of each work period. If you can chat comfortably, you are not working hard enough, and the session becomes a gentle circuit instead. But high intensity is not the same as bad form. When your form breaks down, slow down or stop the exercise. A sloppy push-up done fast is worse than a good push-up done slowly, and an injury ends the habit entirely.
The rest periods deserve respect too. Rest is not wasted time: it is what lets you hit the next work period hard. Stand still, walk slowly or shake out your arms, and breathe deeply. Do not sit down completely if you can avoid it, because standing keeps your heart rate up and makes the next round easier to start. If you need a longer rest, pause the timer rather than guessing. A paused timer keeps the session honest, while a guessed rest quietly turns a six-minute workout into a fifteen-minute ramble.
Here is the honest limit, stated plainly: this timer only runs while this page stays open in your browser. If you close the tab, the workout timer stops. Keep the tab open, keep the device where you can hear the beeps, and do not rely on this tool for a session that must run while you are away from the screen. For a phone workout in the park, a watch timer or a dedicated app that runs in the background is a better choice.
How to use the interval timer
- Set the work seconds, rest seconds and number of rounds.
- Choose your exercises and write their order on a card.
- Warm up for three to five minutes.
- Press Start and follow the WORK and REST phases and the beeps.
- Cool down and stretch when the final round ends.
Frequently asked questions
What is a good beginner setting? Twenty seconds of work, thirty seconds of rest, six rounds, with simple exercises you know well.
How hard should the work periods feel? Hard enough that you are breathing heavily and cannot hold a conversation by the end of each one.
Can I pause mid-workout? Yes. Press Pause, rest properly, and press Start again. The timer keeps your place.
Does the timer run if I close the tab? No. It only runs while this page stays open.
Work hard, rest well, repeat. Set your intervals, press Start, and let the timer call the shots.
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