HIIT Timer

High-intensity interval training alternates short bursts of hard effort with short recovery periods, repeated for a set number of rounds. What separates a full HIIT session from a bare work/rest loop is what sits on either side of the rounds: a warm-up before the first work interval and a cool-down after the last one. This timer expands the entire session into a single phase list — warm-up, then every work and rest interval in order, then cool-down — and runs through that list from start to finish, sounding a distinct tone at each phase change so nothing has to be reset by hand partway through.

Setting up a session

Five number fields define the session and all of them are editable. Warm-up seconds defaults to 60, work seconds to 30, rest seconds to 30, rounds to 10, and cool-down seconds to 60. Entering 0 in the warm-up, rest, or cool-down field removes that phase from the session completely. A warm-up of 0 means the timer opens directly on the first work interval. A cool-down of 0 means the session ends the moment the final work interval does. A rest of 0 puts the work intervals back to back with no gap between rounds. Only the work seconds and the round count need a value above zero for the session to run.

Session length and the skipped final rest

The rest period after the last round is skipped, since the cool-down follows immediately and a recovery gap before it would serve no purpose. That makes the real length of a session slightly shorter than the preset names imply. The default 30/30 across ten rounds is 300 seconds of work plus nine rest periods of 30 seconds, which is 9:30 of interval work rather than a flat ten minutes. Add the default 60-second warm-up and 60-second cool-down and the whole thing runs 11:30. The same arithmetic applies to the other presets: 40/20 for eight rounds is 7:40 of intervals, 45/15 for twelve rounds is 11:45, and 20/40 for eight rounds is 7:20. Knowing the true totals helps when a session has to fit inside a fixed block of time.

The four presets

Tapping a preset fills the fields with a common combination instead of typing the numbers again each session. "Classic 30/30 × 10" is an even split of thirty seconds of work and thirty seconds of rest across ten rounds. "40/20 × 8" keeps the work interval longer than the recovery. "45/15 × 12" narrows the recovery further and adds rounds. "Beginner 20/40 × 8" reverses the pattern so the recovery is twice the length of the effort. Every field stays editable after a preset is applied, so a preset can serve as a starting point that you adjust one value at a time rather than a locked format.

Work-to-rest ratios

Interval formats get renamed constantly, but the 2026 versions still reduce to the same three numbers: how long the effort lasts, how long the recovery lasts, and how many times the pair repeats. HIIT is defined by the ratio between those first two values rather than by any single fixed protocol, which is why the presets look so unlike each other. A 30/30 split is a 1:1 ratio, 40/20 is 2:1, and 45/15 is 3:1 — the work interval stays roughly the same length while the recovery shrinks around it. In the other direction, 20/40 is a 1:2 ratio with recovery running twice as long as the effort. The timer does not enforce a ratio or compare one field against another; it counts exactly the numbers entered. Ratio also drives total time in ways that are easy to misjudge: eight rounds of 40/20 come to 7:40 of intervals, while eight rounds of 20/40 come to 7:20, close totals built from opposite structures.

Why warm-up and cool-down are separate phases

A generic work/rest timer can be pushed into covering a warm-up by treating it as an extra round, but then the round counter is off by one for the remainder of the session and the cue that marks the start of real work sounds the same as every other cue. Here the warm-up and the cool-down sit outside the round loop as phases of their own. The progress line reads "Round 1 of 10" at the first work interval rather than the second, and the round count on screen matches the number that was entered. After the final work interval the cool-down runs as its own labeled phase, then the display reads "Session complete" and a closing beep sounds, so the end of the session is never ambiguous.

Reading the display during a set

The display carries three pieces of information at once: the time remaining in the current phase as MM:SS, the name of the current phase, and a progress line in the form "Round X of Y · MM:SS left of MM:SS", which compares the time left in the whole session against its total length. Fullscreen mode enlarges that display so it can be read from across a room, which matters when the device is on a bench or a windowsill several feet away. Start runs the session, Pause stops the clock and resumes from the exact second it stopped rather than restarting the current phase, and Reset returns everything to the beginning of the phase list with the field values left as they were.

How this differs from the other interval timers here

The interval timer is a plain work/rest loop: one work duration, one rest duration, and a round count, with no warm-up or cool-down phases available at all. The Tabata timer is fixed to a single named protocol — twenty seconds of work, ten seconds of rest, eight rounds, four minutes in total — and is preconfigured precisely because that protocol does not vary. The boxing timer is organized around combat-sports formats, where a round commonly lasts two or three minutes and the rest between rounds is a full minute. This page covers the remaining case: a session whose work-to-rest ratio changes from one workout to the next, and where the warm-up and cool-down are part of what is being timed rather than something happening off the clock.

Related tools

For a bare work/rest cycle with no warm-up or cool-down, use the interval timer. For the strict twenty-ten, eight-round protocol, use the Tabata timer. For round-and-rest formats used in boxing and other combat sports, see the boxing timer. For a single countdown with no phases, use the online timer, and the time tools hub lists every timer and clock on the site.