HIIT · Tabata · circuits
Interval Timer
Work, rest, repeat. Set the two periods and the number of rounds, add a warm-up and cool-down if you want them, and the timer runs the whole session while you concentrate on the effort.
Ready
Space start or pause · S skip · R reset
Work and rest (seconds)
Presets
Options
Session Plan
Common protocols
Interval Patterns Worth Knowing
| Protocol | Work / rest | Rounds | What it is for |
|---|---|---|---|
| Tabata | 20 / 10 s | 8 | Four minutes of genuinely maximal effort. Brutal if done properly. |
| Classic HIIT | 30 / 15 s | 10 | Hard but sustainable. A reasonable place to start. |
| Circuit stations | 45 / 15 s | 12 | Long enough to complete a set at each station and move on. |
| Even intervals | 60 / 30 s | 8 | Running and rowing repeats, where a minute is a natural unit. |
| EMOM | 60 / 0 s | 10–20 | Every minute on the minute: your rest is whatever the work leaves you. |
| Threshold repeats | 2 / 1 min | 5–6 | Longer efforts at a controlled hard pace rather than a sprint. |
| Study sprints | 5 / 1 min | 6 | Nothing to do with exercise; the structure works for drilling too. |
Getting it right
Four Things That Make Intervals Work
The Work Has to Be Hard
The entire benefit comes from the intensity of the work periods. Twenty seconds at a comfortable pace with ten seconds off is not a training stimulus, it is a slightly interrupted walk. If you could hold the pace for five minutes, it is not an interval.
The Rest Has to Be Real
Rest is not wasted time, it is what makes the next work period possible at the same intensity. Cutting the recovery to make the session feel harder usually just makes every round after the second one slower.
Warm up First
Going from sitting to maximum effort in one step is how people get hurt. The warm-up field defaults to ten seconds so the timer does not start mid-round, but a real warm-up before you open the page should be several minutes.
Not Every Day
High-intensity work is demanding enough that two or three sessions a week is plenty for most people, with easier work in between. The adaptation happens during recovery, not during the session.
This is a timer, not a training plan. If you have a heart condition, are pregnant, are returning from injury, or have not exercised in a long time, talk to a doctor or a qualified coach before doing high-intensity work.
Answers
Interval Timer Questions
Tabata, round counts, beeps and using intervals away from the gym.
What is interval training?
Alternating hard effort with recovery, repeatedly. The work periods push you above a comfortable pace and the rest periods let you come back down enough to do it again. It is the structure behind HIIT, Tabata, circuit training and most sprint sessions, and the only thing they really share is that the timing is fixed in advance rather than decided while you are tired.
What is Tabata, exactly?
Twenty seconds of maximum effort and ten seconds of rest, eight times, for a total of four minutes. It comes from a 1996 study led by Izumi Tabata on Japanese speed skaters, and the key detail people usually drop is that the work intervals were genuinely all-out — around 170% of VO2 max. Twenty seconds of moderate effort is not Tabata, it is just a short interval.
Why does the countdown beep before each change?
So you can prepare rather than react. Three short beeps in the last three seconds of every period let you get into position before the switch, which matters when the work interval is only twenty seconds and the first three of them would otherwise be spent getting ready.
How many rounds should I do?
Fewer than you think when you are starting. Eight rounds of twenty and ten is four minutes and is genuinely hard if the effort is real. Most people are better served by adding intensity to a small number of rounds than by adding rounds at a moderate effort.
Can I use this for something other than exercise?
Yes, and people do. Language drills, sight-reading practice, spaced repetition, timed writing sprints, physiotherapy exercises and meditation with timed segments all fit the same shape. Anything alternating effort and pause on a fixed schedule works.
Will it keep running if my phone locks?
Probably not for long. Mobile browsers suspend hidden pages quickly, so keep the screen on during a session. Full screen mode plus your device's longest screen timeout is the reliable setup.
Does the timer drift over a long session?
No. Each period is anchored to a finishing timestamp calculated from the last one rather than counted tick by tick, so errors cannot accumulate across rounds. A forty-round session ends at exactly the right moment.