45s work / 15s rest × 10 rounds
HIIT Timer
Adjustable work and rest intervals for interval training at a hard but sustainable effort.
HIIT
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Frequently asked questions
- How is this different from Tabata?
- Tabata is a fixed, maximal-effort version of HIIT — 20/10 for eight rounds. This HIIT timer lets you set any work, rest, and round count at a sustainable hard effort rather than an all-out one. Use Tabata for four brutal minutes; use HIIT for a longer, adjustable session.
- What work-to-rest ratio should I use?
- For conditioning, shorter rest (2:1 or 3:1, like the 45/15 default) keeps intensity high. For power and speed work, use equal or longer rest (1:1 to 1:2) so each effort stays fast and clean. Match the ratio to the goal.
- How many rounds is enough?
- Ten rounds of 45/15 is about ten minutes of intervals, which is plenty for most people. If you can comfortably do far more, your work intervals probably are not hard enough. Start conservative and add rounds as you adapt.
- Do I need to warm up?
- Yes. Five to ten minutes of easy movement before the first hard interval lowers injury risk and actually improves your output — cold muscles cannot produce their best effort safely.
- Will it keep time if I lock my phone or change apps?
- The count is based on the real end time, so it stays accurate. But a backgrounded tab can delay the audio cue by up to a minute, and a locked or sleeping screen — especially on an iPhone — may not alert you at all; a fully closed tab will not either. Keep the tab open with the screen awake, and on iPhone keep the side mute switch off.
This timer keeps the exact time even if you switch tabs. If this tab or your browser closes, nothing can alert you at the exact finish time — there's no server behind this, by design. Come back any time and we'll tell you honestly how long ago it ended.