Interval Timer
Set how many seconds on, how many off and how many rounds, then leave it. It beeps at every change and announces the round, so you never have to look at the screen mid-set.
Work 1 of 8
00:30
About interval training
Interval work is short hard efforts separated by rest, repeated. The reason it needs a timer rather than a count is that the effort is supposed to be hard enough that you lose track — counting reps yourself is a task, and the whole design is to remove every task except the work.
The ratio of work to rest is what sets the character of the session. Roughly equal work and rest builds the ability to repeat efforts. Rest much longer than the work — twenty seconds on, two minutes off — lets each effort be genuinely maximal, so it trains top-end power. Rest much shorter than the work is a conditioning session and gets brutal quickly, which is why the famous protocols are all short.
Tabata is the best known of those: twenty seconds of very hard work, ten seconds off, eight rounds, four minutes in total. It came out of Izumi Tabata's research on speed skaters in the 1990s and the original was genuinely all-out, at an intensity most people never reach. Almost everything sold as tabata since is a twenty-ten circuit at a comfortable effort, which is a fine workout and not the same thing.
The defaults here are thirty on, fifteen off, eight rounds — six minutes of work, gentle enough to be a warm-up and hard enough to be a session depending on what you put in it. Every field is editable, so tabata is twenty, ten and eight.
What people use it for
- HIIT and tabata sessions
- Circuit training with a fixed time at each station
- Boxing and martial arts rounds
- Physiotherapy and rehab exercises held for a set count
- Stretching routines with a timed hold on each side
How it works
Every phase runs into the next automatically with a beep at each change — a single beep going into rest, a double going into work, so you can tell them apart without looking. The last round finishes with a longer tone.
The phase name shows which round you are on out of how many, and the page changes colour between work and rest, so a glance from across the room is enough.
The end of each phase is scheduled the moment you press start, as an absolute time rather than a delay. On a short interval that matters: a timer that re-arms itself every round accumulates a few milliseconds of error each time, and over sixty rounds the drift is audible.
Changing the work, rest or round fields rebuilds the session from the start rather than altering one mid-flight.
- Space
- Start or pause.
- R
- Reset.
- Tab title
- Shows the time left, so a background tab still tells you.
Questions
What is a tabata timer?
Twenty seconds of work, ten seconds of rest, repeated eight times — four minutes altogether. Set work to 20, rest to 10 and rounds to 8 and this becomes one.
What work-to-rest ratio should I use?
It depends what you are training. Roughly 1:1 builds the ability to repeat efforts. Around 1:3 or more rest lets every effort be maximal, which trains power. Less rest than work is conditioning and gets very hard very fast.
Does it count the rest after the final round?
No. The session ends on the last work interval, because a rest with nothing after it is just standing about.
Can I hear it over music?
The beeps are deliberately pitched high and short so they cut through, but they play through the same output as everything else. If your music is loud the reliable answer is to watch the colour change instead — the page switches between work and rest.
Will it drift over a long session?
No. Each phase boundary is a fixed point in time worked out at the start, not a delay added to the previous one, so sixty rounds ends exactly as far out as one round does.
Can I add a warm-up before the first round?
Not as a separate phase. In practice people set the first work interval longer and treat it as the warm-up, or run a short countdown first and then start this.
How many rounds should a session be?
Eight to twelve is typical for hard intervals, and the total hard work usually lands between four and twenty minutes. If you can comfortably do thirty rounds, the intervals are not intervals — they are steady work with pauses in it.
Does it keep time if my phone screen goes off?
The screen is held awake while a session runs, on browsers that support it. If the screen does go off, the timer still finishes at the right moment because it reads the clock rather than counting.