Fitness age is the age at which your level of cardiorespiratory fitness would be average. If you are 47 but your estimated VO2 max matches the median 38-year-old, your fitness age is 38. It reframes fitness as something you can move in either direction, rather than a number fixed by your birthday.

How is the estimate calculated?

We estimate your VO2 max from your resting heart rate using the Uth method, then find the age at which that VO2 max is the 50th percentile for your sex using the FRIEND registry reference data. It is a transparent, fully referenced estimate, not a clinical measurement.

How can I lower my fitness age?

Improve your cardiorespiratory fitness. A mix of easy aerobic volume and a smaller dose of harder intervals, progressed over months and supported by strength training, reliably raises VO2 max. As your VO2 max rises, your fitness age falls. A re-test is how you confirm it is working.

The Big Picture

Fitness Age Calculator

Your birthday is fixed. Your fitness age is not. Enter your age and resting heart rate to see the age at which your cardiorespiratory fitness would be average, benchmarked against the FRIEND registry.

Why fitness age is the number that moves

Most health numbers feel fixed. Fitness age is different: it is a single, intuitive read on cardiorespiratory fitness, the capacity most tightly linked to a long healthspan, and it responds directly to training. Watching it fall over a training block is one of the most motivating feedback loops in fitness. This calculator gives you the quick cardiorespiratory estimate. The full version, across all four pillars on the same scale we use in studio, is the free Healthspan Audit.

Average (median) VO2 max by age

Fitness age works by comparing your estimated VO2 max to the median for each age. These are the 50th-percentile treadmill values from the FRIEND registry (ml/kg/min). If your estimate matches the median for a younger age, that age is your fitness age.

Age	Men (median)	Women (median)
20 to 29	48	37.6
30 to 39	42.4	30.2
40 to 49	37.8	26.7
50 to 59	32.6	23.4
60 to 69	28.2	20
70 and over	24.4	18.3

Fitness age, common questions

What is fitness age?: Fitness age is the age at which your level of cardiorespiratory fitness would be average. If you are 47 but your estimated VO2 max matches the median 38-year-old, your fitness age is 38. It reframes fitness as something you can move in either direction, rather than a number fixed by your birthday.
How is the estimate calculated?: We estimate your VO2 max from your resting heart rate using the Uth method, then find the age at which that VO2 max is the 50th percentile for your sex using the FRIEND registry reference data. It is a transparent, fully referenced estimate, not a clinical measurement.
How can I lower my fitness age?: Improve your cardiorespiratory fitness. A mix of easy aerobic volume and a smaller dose of harder intervals, progressed over months and supported by strength training, reliably raises VO2 max. As your VO2 max rises, your fitness age falls. A re-test is how you confirm it is working.

More free Healthspan calculators

Cardiorespiratory

VO2 Max Calculator →

Strength

Grip Strength Test →

Body Composition

Waist-to-Height Ratio →

Stability

Sitting-Rising Test →

All calculators + the Healthspan Audit →

Catalyst Performance

Fitness Age Calculator

Why fitness age is the number that moves

Average (median) VO2 max by age

Age	Men (median)	Women (median)
20 to 29	48	37.6
30 to 39	42.4	30.2
40 to 49	37.8	26.7
50 to 59	32.6	23.4
60 to 69	28.2	20
70 and over	24.4	18.3

Fitness age, common questions

What is fitness age?: Fitness age is the age at which your level of cardiorespiratory fitness would be average. If you are 47 but your estimated VO2 max matches the median 38-year-old, your fitness age is 38. It reframes fitness as something you can move in either direction, rather than a number fixed by your birthday.
How is the estimate calculated?: We estimate your VO2 max from your resting heart rate using the Uth method, then find the age at which that VO2 max is the 50th percentile for your sex using the FRIEND registry reference data. It is a transparent, fully referenced estimate, not a clinical measurement.
How can I lower my fitness age?: Improve your cardiorespiratory fitness. A mix of easy aerobic volume and a smaller dose of harder intervals, progressed over months and supported by strength training, reliably raises VO2 max. As your VO2 max rises, your fitness age falls. A re-test is how you confirm it is working.