Fitness age from the NTNU method.
A non-exercise VO2max estimate from waist, resting heart rate, and activity, then mapped onto HUNT reference fitness by age. Or type a lab or watch VO2max and skip the estimate.
NTNU non-exercise estimate
Age, sex, waist, resting heart rate, and three activity questions. Or skip the estimate and type a lab or watch VO2max. The result is an estimated fitness age.
An estimated fitness age and VO2max show up here.
- VO2max
Longevity Arc - Vs your age
Metrya - Activity
DeskWalker
What moves this number: lower waist and resting heart rate, and more frequent or harder sessions raise estimated VO2max. Grip and daily steps are not inputs here — see the dead hang and walking pad calculators. 
Hang Tracker
How it's calculated
Unless you enter a measured or watch VO2max, the page estimates VO2peak in ml/kg/min with the Nes 2011 HUNT waist model. For men: 100.27 − 0.296×age − 0.369×waist(cm) − 0.155×resting heart rate + 0.226×PA index. For women: 74.74 − 0.247×age − 0.259×waist − 0.114×resting heart rate + 0.198×PA index. The PA index is frequency × duration × intensity, using the same response weights as the CERG/NTNU Fitness Calculator.
Fitness age is the age whose HUNT reference VO2peak matches that number. This page uses the CERG linear maps: men 160.7 − 2.513×VO2max; women 155.8 − 3.049×VO2max. The result is rounded to a whole year and held between 20 and 90. When the raw map sits outside that range, the page says so.
Sources: Nes BM, Janszky I, Vatten LJ, Nilsen TIL, Aspenes ST, Wisløff U. Med Sci Sports Exerc. 2011. Nes BM, Vatten LJ, Nauman J, Janszky I, Wisløff U. Med Sci Sports Exerc. 2014. Reference means: Loe H, Steinshamn S, Wisløff U. PLoS ONE. 2014.
General information, not medical advice. Talk to a clinician about health decisions.
Common questions
What is fitness age?
It is the age at which the typical HUNT Fitness Study VO2peak for your sex matches your estimated (or entered) VO2max. If that age is lower than your calendar age, your number sits with a younger reference group. The map is clamped between 20 and 90.
How accurate is a non-exercise estimate?
The Nes 2011 waist model explained about 61% of VO2peak variance in men and 56% in women, with a standard error near 5.7 and 5.1 ml/kg/min. Read the result as a rough band, not a lab reading. Extremes of fitness are where non-exercise models drift most.
Why waist and resting heart rate?
In the HUNT sample those two measures, with age and the activity index, carried most of the explained variance for VO2peak. Waist edged out BMI slightly in men. Resting heart rate added a smaller but clear amount after age, waist, and activity were in the model.
Can I use an Apple Watch VO2max?
Yes. Choose “I already have a VO2max” and type the watch number. That skips the waist and activity estimate. The fitness age still uses the same HUNT age map. A watch figure is not the same measurement as a lab VO2peak.
How do I raise my fitness age?
In this method, a younger fitness age follows a higher VO2max. More frequent or harder sessions raise the activity index. A smaller waist and a lower resting heart rate also raise the non-exercise estimate. Training that raises measured VO2max moves a typed lab or watch number the same way.
Other calculators: VO2max by age · Dead hang test · Walking pad steps