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.
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Round 1 / 12
⚙️ Customize Timer
Work
Rest
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.
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❓ Frequently Asked Questions
How do I create a custom interval timer?
Use the settings panel on the right to enter your desired Rounds, Round Time (MM:SS), Rest Time (MM:SS), Prepare time (the countdown before round 1), and Warning time (audio cue before each round ends). Click Apply to update the timer, then Start to begin.
Can I change the settings while the timer is running?
Change settings while paused or stopped. Click Reset first, update your settings, click Apply, then Start. Changing settings mid-round is not recommended as it resets the current round's progress.
What is the Prepare countdown?
The Prepare phase is a countdown before round 1 begins — useful for getting into position, attaching gloves, or steadying breathing. Common prepare times: 10 seconds for fitness, 25 seconds for boxing, 0 seconds for study sessions.
What is the Round End Warning?
The warning plays an audio cue N seconds before each round ends — giving you time to prepare for the rest phase or push for a final effort. A 10-second warning is standard in boxing; 3 seconds is common for HIIT workouts.
What work-to-rest ratio should I use?
Ratio by goal: 1:1 (30:30) for general fitness; 2:1 (40:20 or 20:10 Tabata) for high intensity; 3:1 (45:15) for strength-endurance; 1:3 (20:60) for power/speed work with full recovery. Beginners should start with at least 1:1.
How many rounds should I set?
Rounds by duration: 6–8 rounds for a 4–8 minute focused block; 10–12 rounds for a 15–20 minute workout; 20+ rounds for extended conditioning sessions. For Tabata: exactly 8 rounds per exercise.
Can I use this for non-fitness activities?
Yes — the custom interval timer works for any timed activity: study sessions (50 min work / 10 min break), meeting timekeeping, language practice drills, music practice intervals, and debate prep. Set Prepare and Rest to 0 for a simple repeating work timer.
Does the timer work without internet?
Once the page has loaded, the timer runs entirely in your browser using JavaScript — no internet connection required. The sounds are generated by the Web Audio API. Save the page as a browser bookmark and it will work offline.