What VO&sub2; max is
VO&sub2; max is the maximum amount of oxygen your body can take in and use during all-out exercise, measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It's the single best measure of aerobic fitness — and one of the strongest predictors of endurance performance and long-term health.
The fitter your heart, lungs and muscles are at delivering and using oxygen, the higher your VO&sub2; max, and the longer you can sustain hard effort.
How we estimate it
The most accurate VO&sub2; max test happens in a lab with a mask and treadmill. This calculator uses a well-validated shortcut — the Uth–Sørensen formula, which estimates VO&sub2; max as 15.3 × (maximum heart rate ÷ resting heart rate). Because it leans on your resting heart rate, an accurate resting reading (taken first thing in the morning) gives the best estimate.
What counts as a good score
VO&sub2; max varies with age and sex, declining gradually as we get older. As a rough guide, an untrained adult might score in the low 30s, a recreationally fit adult in the 40s, and elite endurance athletes well above 60. The result above rates your estimate against typical values for your sex.
Improving your VO&sub2; max
Two ingredients raise VO&sub2; max: a big base of easy aerobic miles (Zone 2) and regular high-intensity intervals that push you near your ceiling. Classic sessions are 4×4-minute hard efforts or shorter 30-second repeats, done once or twice a week on top of easy training. Consistency over months is what moves the number.
Helpful tools
Many watches estimate and track VO₂ max trends over time.
View options →Get the accurate resting and exercise readings these estimates rely on.
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Frequently asked questions
What is a good VO₂ max?
It depends on age and sex, but broadly: the 30s are below average, the 40s are good, and above 50–60 is excellent to elite. The calculator rates your estimate against typical values.
How accurate is a heart-rate VO₂ max estimate?
The Uth–Sørensen method correlates well with lab tests at a population level, but it's still an estimate. Use it to track your own progress rather than as an exact clinical figure.
How can I improve my VO₂ max?
Combine a large volume of easy aerobic exercise with regular high-intensity intervals. Both raise your heart's stroke volume and your muscles' ability to use oxygen.
Does VO₂ max decline with age?
Yes, gradually from around the late 20s, but regular endurance training slows the decline significantly and can keep your fitness well above your age group.