How to use the interval timer (hiit and tabata)
- Pick a format button such as Tabata to load example times, or type your own: warm up, work, rest, rounds per set, sets, rest between sets and cool down. All times are whole seconds.
- Check the total time shown under the settings, then press Start. The clock counts down the current phase and the box changes color for work, rest and warm up.
- Use Pause to stop the clock and Resume to carry on, Skip to jump to the next phase, and Reset to go back to the start with the same settings.
- Leave the sound option on to hear a beep at the start of each phase and on the last three seconds, or turn it off for a silent timer.
How the workout is laid out
A workout is a warm up, then one or more sets, then a cool down. Each set holds the number of rounds you choose, and each round is one work interval followed by one rest interval. The timer leaves out the rest after the very last round, because there is nothing left to rest for, and it uses the longer rest between sets in place of the normal rest after the last round of a set.
For example, a two set workout with 8 rounds per set has 16 work intervals, 14 normal rests and one rest between sets. The total shown under the settings adds all of these together so you know the full length before you start.
Common formats you can load
The buttons load example formats, and every number can be edited. Tabata here means 20 seconds of work and 10 seconds of rest for 8 rounds, with a short warm up. The 30 on, 30 off format repeats a half minute of effort and a half minute of rest ten times. The 40 on, 20 off format runs two sets with a minute between them. The 3 minute rounds format has twelve three minute rounds with one minute of rest, which suits boxing style work.
These are starting points rather than prescriptions. Choose work and rest times that match your fitness and what your coach or doctor has told you. If you are not sure whether a hard interval workout is right for you, ask a health professional first. You can also check your effort with the heart rate zone calculator.
Why it stays accurate in a background tab
The timer does not count ticks. It records when each stretch of running began and works out how much time has passed by comparing clock readings, so a busy page or a tab in the background does not make the countdown drift. If the browser pauses the page for a while, the clock catches up the next time it runs. Phones and tablets that lock the screen may stop the sound until you wake the device, so keep the screen on during a workout.
Sound is made with the browser's built in audio and only starts after you press Start, never when the page loads. Nothing is saved and nothing you enter leaves your device. For a plain countdown use the online timer, and for focused work with breaks try the Pomodoro timer.
Assumptions and limits
- Times are whole seconds, from 1 to 3,600 for work and from 0 to 3,600 for the other times. A workout can be at most 24 hours long.
- The formats on the buttons are examples that you can change. They are not recommendations for any person.
- Beeps depend on your device allowing sound. The visual clock and the screen reader announcements work without sound.
- Settings are not saved. Reloading the page returns to the Tabata example.
Frequently asked questions
What is a Tabata timer?
In this timer, Tabata is a preset of 20 seconds of work and 10 seconds of rest repeated for 8 rounds, which takes about 4 minutes. The timer adds a short warm up in front. You can change every value if you want a different format.
Does the interval timer keep running if I switch tabs?
Yes. It measures real elapsed time instead of counting ticks, so the countdown stays correct when the tab is in the background. Some phones stop sound and timers when the screen locks, so keep the screen awake while you train.
Can I use it for boxing rounds or circuit training?
Yes. Set the work time to the length of a round, the rest time to the break, and the rounds to the number you need. Use sets and the rest between sets to group stations or circuits.
Why is there no rest after my last round?
The timer ends a workout on the final work interval, or on the cool down if you add one, because resting after the last round does not help you. To add a rest anyway, put it in the cool down box.