About the Fitness Age Calculator
Your fitness age is the age at which an average person has the same cardiorespiratory fitness (VO2 max) as you. A 50-year-old with the aerobic fitness of a typical 40-year-old has a fitness age of 40. This calculator estimates it without a lab test, using a non-exercise model built from four things you can measure at home: age, waist circumference, resting heart rate and how often, how long and how hard you exercise.
It is a quick motivation check for anyone starting or restarting exercise, and a way to track progress over months as your resting heart rate falls and your waistline shrinks. Because it needs no treadmill or watch test, it works for almost everyone.
The VO2 max estimate follows the structure of the non-exercise model from Norway’s HUNT fitness study (Nes et al., 2011), and fitness age is read from an approximate linear curve of average VO2 max by age. It is an estimate, typically within several ml/kg/min of a lab test, not a medical assessment.
With the default inputs, the fitness age is 49 years. Change any value above to recalculate instantly.
How to use the fitness age calculator
- 1Select your sex and enter your age.
- 2Measure your waist at the navel in centimetres.
- 3Take your resting heart rate on waking, sitting quietly for a minute.
- 4Choose how often, how hard and how long you usually exercise.
- 5Read your fitness age and estimated VO2 max.
Formula and method
VO2 max is estimated with a non-exercise regression of the form published from the HUNT fitness study, using age in years, waist in cm, resting heart rate in bpm and a physical activity index PA = frequency × intensity × duration scores (for example 2.5 × 5 × 0.75 = 9.4 for hard 30–60 minute sessions two to three times a week).
Fitness age is then the age at which the approximate population-average VO2 max equals your estimate. Average VO2 max is modelled as 64.0 − 0.38 × age for men and 50.4 − 0.294 × age for women, a linear fit to typical reference values; the result is rounded and limited to 18–90 years.
- Waist
- Waist circumference in centimetres
- RHR
- Resting heart rate in beats per minute
- PA
- Activity index = frequency × intensity × duration scores
Worked examples
45-year-old man, exercises hard 2–3 times a week
PA = 2.5 × 5 × 0.75 = 9.375. VO2 = 100.27 − 13.32 (age) − 33.95 (92 cm waist) − 9.92 (64 bpm) + 2.12 = 45.2 ml/kg/min. The average man hits 45.2 at about 49, so his fitness age is 49 — four years older than his real age, mainly because of the waist measurement.
Same man after training almost daily
Training hard almost every day doubles the activity index to 18.75, and a 7 cm smaller waist plus a resting pulse of 56 lift the estimate to 51.1 ml/kg/min. That is the average for a 34-year-old, a fitness age 11 years below his real age.
60-year-old woman who trains daily for over an hour
Her activity index is 5 × 5 × 1 = 25. VO2 = 74.74 − 14.82 − 20.72 − 6.84 + 4.95 = 37.3 ml/kg/min, well above the 32.8 average for her age and equal to a typical 45-year-old woman.
Frequently asked questions
What does fitness age mean?+
Fitness age is the age at which an average person of your sex has the same VO2 max (aerobic fitness) as you. It reflects cardiovascular fitness, not how old your cells or organs are, but low fitness is strongly linked to higher health risk.
How accurate is a fitness age calculator?+
Non-exercise models like this one explain a large share of the differences in VO2 max between people, but individual estimates can be off by several ml/kg/min. A treadmill or cycle test with gas analysis is the gold standard.
How can I lower my fitness age?+
Regular vigorous exercise that makes you breathless — for example interval training two to three times a week — improves VO2 max most. Reducing waist size and lowering resting heart rate through training also improve the estimate.
How do I measure my resting heart rate?+
Measure it in the morning before getting up or after sitting quietly for several minutes. Count your pulse for 30 seconds and double it, or use the reading from a reliable watch or chest strap.
Why does waist size affect fitness age?+
VO2 max is expressed per kilogram of body weight, and waist circumference is a strong marker of body fat. Extra fat raises body weight without adding oxygen-using muscle, which lowers VO2 max per kilogram.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.