Session length
With 0:40 work and 0:20 rest per round (plus a 10-second get-ready countdown), the whole session lasts:
| Rounds | Total time |
|---|---|
| 4 | 3:50 |
| 6 | 5:50 |
| 8 | 7:50 |
| 10 | 9:50 |
| 12 | 11:50 |
| 16 | 15:50 |
| 20 | 19:50 |
How to use the interval timer
Set how long each work interval lasts, how long you rest between intervals, and how many rounds you want, then press Start. You get a get-ready countdown first, a beep at every change between work and rest, and three short beeps before each change so you are never caught off guard.
Your settings are saved in the page address. Bookmark the page after setting it up and the same workout opens next time.
Common interval setups
- 40 / 20 — 40 seconds work, 20 seconds rest. A common circuit-training format.
- 30 / 30 — equal work and rest, easier to sustain for longer sessions.
- 45 / 15 — short rest for conditioning blocks.
- Running intervals — for example 60 seconds fast, 90 seconds easy, 8 rounds.
Not sure what to set?
The settings guide matches work, rest and rounds to your goal. New to exercise? Start with how to start working out and the 4-week HIIT beginner plan. Runners: see walk/run intervals. All guides are listed on the guides page.
Read next: Interval Work-to-Rest Ratios: 20/10, 30/30, 40/20, 45/15 Compared
FAQ
What is an interval timer?
An interval timer alternates between work and rest periods for a set number of rounds and signals each change with a sound. You set the work time, rest time and rounds once, then train without watching a clock.
Is this interval timer free?
Yes. WorkoutBell is free, runs in the browser on phone or computer, and needs no app or account. It is supported by ads.
Does the screen stay on during the workout?
On browsers that support the Screen Wake Lock API, the timer keeps your screen on while it runs. The countdown follows the real clock, so it stays accurate even if the tab is in the background.
Popular presets
- 3 Round Boxing Timer — 3 x 3:00, 1:00 rest
- 30 / 10 Interval Timer — 30s on, 10s off
- 30 / 30 Interval Timer — 30s on, 30s off
- 30 / 15 Interval Timer — 30s on, 15s off
- 45 / 15 HIIT Timer — 45s on, 15s off
- 1 Minute Interval Timer — 60s on, 10s off