Customizable interval timer for Tabata, HIIT, and circuit training with audio cues and round tracking.
An interval timer turns a workout plan into a sequence of timed blocks and announces each switch with a sound, so you can keep your eyes on the exercise instead of a clock. You set the work duration, the rest duration, and the round count; the tool then counts down the whole session while showing the current phase and round number. The most common surprise is the scale: the classic Tabata protocol - 20 seconds of effort, 10 seconds of rest, 8 rounds - is over in exactly 4 minutes. The total shown before you start includes the rest block after the last work block.
A concrete input and expected output from the current implementation.
Input
Work 20 s, rest 10 s, 8 rounds
Expected output
Session total 4:00 (240 s): 8 work blocks of 20 s alternate with 8 rest blocks of 10 s, for 160 s of work and 80 s of rest. A cue sounds at every switch, the round counter advances at the start of each work block, and the countdown runs the full 8 rounds.
Each round is 30 s (20 s work plus 10 s rest), so 8 rounds total 240 s, which is exactly 4 minutes. That total is what the timer counts down, which is why the whole protocol is over so quickly.
You enter three numbers - work duration, rest duration, and round count - and the session total is rounds x (work + rest), plus any prep or lead-in the tool offers. That total, shown before you start, is what the countdown runs end to end, including the rest block after the final work block.
While the countdown runs, the timer flips between work and rest automatically: a sound marks each switch, the active phase with its remaining seconds stays on screen, and the round counter increments when a new work block starts. Audio is the main signal, so keep the volume up; the cue only helps if you can hear it.
Every round counts work plus rest, and the timer runs all of them: 8 rounds of 20 s work + 10 s rest total 240 s (4:00), even though the pure work time is only 160 s (2:40). The rest after the final work block is part of the countdown too. Stop the timer yourself if you want to end on the last work beat.
Yes - work and rest durations are free settings, so any ratio works; 45/15 across 6 rounds runs 6 x 60 s, or 6:00. Nothing restricts the tool to the 20/10 ratio. What you give up is only the label: 'Tabata' refers to a specific published protocol, so a modified session should not be compared with it.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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