Apple Health metrics › VO2 Max (Cardio Fitness)

VO2 Max (Cardio Fitness) on Apple Watch and iPhone

An estimate of the most oxygen your body can use during hard exercise, a strong predictor of long-term health.

What it is

VO2 max reflects aerobic fitness. Apple Health shows it as Cardio Fitness, and it is one of the better single markers of how fit your heart and lungs are.

How Apple measures it

Apple Watch estimates it from heart rate and motion during outdoor walks, runs and hikes. It is an estimate, not a lab test, and needs a few qualifying workouts to appear.

What's a normal range?

Values depend heavily on age and sex. As a rough guide, many adults land between 30 and 50 mL/kg/min, and trained endurance athletes score far higher. Apple labels results Low, Below Average, Above Average or High for your age and sex.

What moves it

• Regular aerobic training (raises it)
• Interval training
• Weight loss
• Age (declines slowly)
• Long breaks from exercise

See VO2 Max (Cardio Fitness) next to your other vitals

Apple Health keeps this number several taps deep. OnlyVitals puts the metrics you pick, including VO2 Max (Cardio Fitness), on a single dashboard so you can read them at a glance. Everything stays on your device.

Frequently asked questions

How accurate is Apple Watch VO2 max?

Apple reports that its estimate tracks lab measurements reasonably well in validation, but it is still an estimate. Watch the trend over months rather than single readings.

Why doesn't my Apple Watch show VO2 max?

It needs outdoor walking, running or hiking workouts with GPS and a recent heart rate history. Make sure your height, weight, age and sex are filled in under Health Details.

Related metrics

• Blood Oxygen (SpO2)
• Respiratory Rate
• Steps
• Sleep Duration
• REM Sleep
• Deep Sleep

This page is general information, not medical advice. Ranges vary by age, sex, fitness and device. Talk to a clinician about anything that worries you.