Apple VO2max: how it works.
Measures how hard your heart works (heart and motion sensors, GPS) during outdoor walks, runs and hikes, plus passive outdoor walking. It also uses your age, sex, weight, height and heart-rate medications.
What counts towards your VO2max
Estimated from: Outdoor run, Walk, All-day data. Not used: Treadmill.
What you need to do
Wear the watch for at least 24 hours, then do several Outdoor Walk, Outdoor Run or Hiking workouts in the Workout app. Fairly flat ground, good GPS and heart rate signal help.
How it is shown
VO2 max in mL/kg/min in the Health app (range 14-65), with a cardio fitness level compared to your age and sex. Levels are for users 20 and older.
Related features
- Fitness age: not confirmed
- Race predictor: not confirmed
- Low cardio fitness notifications
- Training Load
- Effort rating
- Readiness score (Series 12)
Models
Apple Watch Series 12 · Apple Watch Ultra 4 · Apple Watch Series 11 · Apple Watch Ultra 3
How accurate is it?
| Study | Finding |
|---|---|
| Lambe et al., Mayo Clin Proc Digit Health, 2026 | Series 10 underestimated VO2max by 6.25 ml/kg/min on average; MAPE 13.2%; poor individual agreement. |
| Lambe et al., PLoS One, 2025 | Apple Watch underestimated VO2max by 6.07 ml/kg/min on average; MAPE 13.31%. |
| Caserman et al., JMIR Biomed Eng, 2024 | Series 7 estimate was lower than the lab value (41.37 vs 45.88 ml/kg/min); MAPE 15.79%, ICC 0.47. |
Indoor workouts, including gym equipment, do not count; Push workouts are not supported. Tell the Health app if you take beta blockers or calcium channel blockers, or the estimate can be too high. Apple's own 2021 white paper reports a mean error of 1.4 ± 4.7 ml/kg/min against submaximal lab tests in its validation group; independent studies found larger errors.
Frequently asked questions
How does Apple calculate VO2max?
Measures how hard your heart works (heart and motion sensors, GPS) during outdoor walks, runs and hikes, plus passive outdoor walking. It also uses your age, sex, weight, height and heart-rate medications. Wear the watch for at least 24 hours, then do several Outdoor Walk, Outdoor Run or Hiking workouts in the Workout app. Fairly flat ground, good GPS and heart rate signal help.
How accurate is Apple VO2max?
3 published studies have tested it: Series 10 underestimated VO2max by 6.25 ml/kg/min on average; MAPE 13.2%; poor individual agreement.
Which Apple devices show VO2max?
Examples: Apple Watch Series 12, Apple Watch Ultra 4, Apple Watch Series 11, Apple Watch Ultra 3. Support depends on model and firmware.
Check your number against the norms for your age, estimate it with the VO2max calculator, or turn it into race times and paces.
Sources
- Apple Support: Track your cardio fitness levels
- Apple white paper: Using Apple Watch to Estimate Cardio Fitness with VO2 max (May 2021)
- Apple Watch User Guide: Track your training load
- Apple Newsroom: Introducing Apple Watch Series 12 (Sept 2026)
Apple is a trademark of its owner. VO2max Health is independent and not affiliated with Apple. Features vary by model and firmware.