VO2 max is one of the strongest single markers of cardiovascular fitness, and it is now a headline number on most smartwatches. Use this calculator to estimate yours from your resting heart rate or a simple 12-minute run test, then see where you stand for your age and sex.

VO2 Max Calculator

What Is VO2 Max?

VO2 max is the maximum amount of oxygen your body can use during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). A higher number means your heart, lungs, and muscles work together more efficiently. It is closely linked to endurance performance and, in large population studies, to long-term health.

How This Calculator Estimates It

Resting heart rate method. This uses the Uth-Sorensen formula: 15.3 x (max heart rate / resting heart rate), with max heart rate estimated from your age. It needs no exercise at all, which makes it a handy starting point, but it is the least precise option because resting heart rate is affected by sleep, stress, and caffeine.

12-minute run (Cooper test). Run as far as you can in 12 minutes on a flat track or treadmill, then enter the distance. The formula (meters – 504.9) / 44.73 has been used by coaches and the military for decades. It tends to be more accurate than the resting method, as long as you pace the effort evenly and give it a true hard try.

If you are not sure what your heart rate zones look like yet, try our Heart Rate Zone Calculator first. It uses the same max heart rate estimate.

VO2 Max Ratings by Age

The ranges below are approximate and adapted from widely published fitness norms. Values are in ml/kg/min.

Age Men: Good Men: Excellent Women: Good Women: Excellent
20-29 42-45 46-51 36-39 40-45
30-39 40-43 44-49 34-37 38-43
40-49 38-41 42-47 32-35 36-40
50-59 35-38 39-44 29-32 33-37
60+ 32-35 36-41 27-30 31-34

How Smartwatches Measure VO2 Max

Watches do not measure oxygen directly. They combine GPS pace, heart rate, and your profile data during outdoor walks or runs, then model how much effort a given speed costs you. Apple Watch reports it as Cardio Fitness, Garmin and Amazfit show a VO2 max score, and Fitbit and Google Pixel Watch use a Cardio Fitness Score. The number usually needs several outdoor workouts before it settles, and it is most useful as a trend over weeks rather than a single reading.

How to Improve Your VO2 Max

Consistent aerobic training builds the base, and one or two sessions a week of harder intervals push the ceiling higher. A common approach is to keep most training easy and add intervals such as 4 x 4 minutes at a hard but controlled effort with 3 minutes of easy recovery. Losing excess body weight also raises VO2 max, since the number is expressed per kilogram.

Disclaimer: This calculator gives an estimate for general fitness purposes only. A lab test with gas analysis is the only direct measurement. It is not medical advice. Talk with a healthcare provider before making major changes to your exercise, diet, or sleep, especially if you have a health condition or take medication.