Custom Interval Timer
Build your own interval timer — set rounds, work time, rest time, prepare countdown, and end warning. Free, no signup, works in any browser.
⚙️ Customize Timer
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A custom interval timer lets you define every variable of your workout: how long each work phase lasts, how long you rest, how many rounds to complete, and how much preparation time you need before the first round begins. This flexibility makes it suitable for boxing, HIIT, yoga, circuit training, study sessions, and any other timed activity.
No two athletes, coaches, or practitioners have identical needs. The custom interval timer removes the constraint of pre-built protocols and lets you dial in exactly the timing that matches your training program, periodization plan, or work-rest requirements.
Build the interval around the movement
The interval should come from what you are doing rather than from a round number. A movement with a long setup — getting into position, gripping a bar — needs a longer work period to get the same working time as one you can start instantly.
The same applies to rest. A movement that leaves you breathing hard needs recovery measured against the breathing, not against a figure that looked tidy when you set the timer up.
Test it once before committing to the session
A ratio that looks right on paper frequently is not. Running one round before starting the full session costs forty seconds and prevents discovering at round six that the rest was fifteen seconds short.
The signal to watch is whether the last two rounds hold the same quality as the first two. If output falls away, the rest was too short or the round count too high, and the session trained fatigue rather than what you intended.
Preparation time exists for a reason
A ten- or fifteen-second lead-in lets you get into position, start a recording, or simply put the phone down before the first round begins. Without it the first round is always compromised.
It matters most for movements where starting badly is unsafe — anything loaded, anything overhead. Scrambling into position as the beep goes is how the first rep becomes the worst one.
A starting point by goal. Test one round before committing to a full session.
| Goal | Work | Rest | Rounds | Note |
|---|---|---|---|---|
| Strength | 20-30 s | 90-180 s | 5-8 | Quality over density |
| Power | 10-20 s | 2-3 min | 6-10 | Every rep maximal |
| Conditioning | 40 s | 20 s | 8-12 | Density is the point |
| Endurance | 60-90 s | 30 s | 6-10 | — |
| Skill practice | 60 s | 30 s | 6-10 | Stop before form goes |
| Preparation | 10-15 s | — | — | Set up before round one |
- Build the interval from the movement — a long setup needs a longer work period for the same working time.
- If the last two rounds are visibly worse than the first two, the rest was short or the round count high.
Source: Interval structures are established training convention rather than a published standard
Sources
- Interval structures are established training convention rather than a published standard , TheTimerLab — accessed 2026-07-28