VO₂max.io

Free interval timer

Interval timer

Set work time, rest time and rounds. The timer beeps before each change, shows what comes next and keeps your phone screen on.

Interval timer

Warm-up
0:00
Next up
Total
Work intervals

Beeps 3 seconds before each change. Keeps the screen awake where the browser allows it.

Heart problems? Check with a doctor before hard intervals or a maximal test if you have heart problems. Stop if you feel chest pain or dizziness.

How to use it

  1. Set your work and rest times and how many rounds.
  2. Press Start, then Full screen if you want big numbers.
  3. Listen for the beeps: three seconds before each change, and a longer beep when it changes.

Ready-made sessions: Norwegian 4×4, 30/30, Tabata, HIIT exercises at home.

The sound starts after you press Start, because phones only allow sound after a tap. Turn off silent mode on iPhone to hear the beeps.

More interval tools

Beep & Cooper test calculator

Your VO₂ max and rating for age and sex.

Norwegian 4×4

4 × 4 min hard, 3 min easy.

30/30 intervals

Run 30 s, walk 30 s.

Tabata 20/10

8 × 20 s all-out, 10 s rest.

HIIT twice a week

Two 20-minute sessions.

HIIT exercises at home

No equipment, with timer.

FAQ

Does the timer work with the screen off?

Keep the page open. The timer asks the phone to keep the screen awake while it runs. If the screen locks, it continues from the right time when you come back.

Is anything saved or sent?

No. The timer runs in your browser and nothing is sent anywhere.

Last updated: October 24, 2026. Written with AI assistance.