How old is your body?

How the test works

Your body's age is your fitness age: the age at which the average healthy woman or man has the same fitness as you. Researchers at the Norwegian University of Science and Technology (NTNU) measured VO₂ max directly in 4,637 healthy adults in the HUNT study and built a formula that estimates it from sex, age, waist, resting heart rate and how often, how hard and how long you exercise (Nes et al., 2011).

The averages for each age come from max tests on 3,816 healthy men and women aged 20–90 in HUNT3 (Loe et al., 2013). Fitness is one of the strongest markers of long-term health: in 37,112 healthy adults in the first HUNT study, every 1 MET higher estimated fitness went with a 21% lower risk of dying from cardiovascular disease among those under 60 (Nes et al., 2014).

The formula is accurate on average, but the standard error is 5.7 ml/kg/min for men and 5.1 for women. For one person, that can mean 10–15 years of fitness age in either direction, so watch how your number changes over time rather than the single result.

Average VO₂ max (ml/kg/min, mean ± SD) for healthy adults in HUNT3:

Age	Women	Men
20–29	43.0 ± 7.7	54.4 ± 8.4
30–39	40.0 ± 6.8	49.1 ± 7.5
40–49	38.4 ± 6.9	47.2 ± 7.7
50–59	34.4 ± 5.7	42.6 ± 7.4
60–69	31.1 ± 5.1	39.2 ± 6.7
70+	28.3 ± 5.2	35.3 ± 6.5

The biohealth score

The biohealth score is our own scoring system, based on WHO's guidelines for physical activity and diet and the recommended 7–9 hours of sleep. Each of the six areas gets 0–100 points, and the score is the average. The tips come from the areas where you have the most to gain.

Area	Full points when you
Fitness	are fitter than almost all healthy people your age in HUNT3. The points are the share you beat.
Movement	are active at least 300 minutes a week (vigorous exercise counts double), do strength training at least two days a week and sit less than 5 hours a day.
Sleep	sleep 7–9 hours and almost always wake up rested.
Light and body clock	are out in daylight more than 30 minutes before noon and rarely use a screen in the last hour before sleep.
Diet	eat at least five portions of fruit, berries and vegetables a day and rarely eat ultra-processed food.
Recovery	rarely feel stressed, do not drink alcohol and do not smoke.

Frequently asked questions

How can I test my biological age?

The simplest way is a test like this one, which estimates your fitness age from your age, waist, resting heart rate and exercise. Epigenetic tests analyse a blood or saliva sample, but different tests can give quite different results for the same person. Whatever the method, the change over time says the most.

What is fitness age?

Fitness age is the age at which the average healthy woman or man has the same fitness as you. If your VO₂ max matches the average 35-year-old, your fitness age is 35, whatever your actual age.

What is the difference between biological age and fitness age?

Biological age is an umbrella term for how old your body seems, and it can be estimated in many ways, from DNA, blood tests or fitness. Fitness age is one of them, based on how well your heart, lungs and muscles take up and use oxygen.

How accurate is the test?

The formula is accurate on average but can miss for one person. The standard error is 5.7 ml/kg/min for men and 5.1 for women, which can mean 10–15 years of fitness age either way. A max test on a treadmill or bike gives a more precise number.

How do I lower my biological age?

Do intervals once or twice a week, for example NTNU's 4x4: four 4-minute intervals at 90–95% of your max heart rate with 3 minutes of easy activity between. In a study, 4x4 raised VO₂ max by 7.2% in eight weeks. A smaller waist and a lower resting heart rate also lower the number.

Are my answers stored?

Not by us. Everything is calculated in your browser, and nothing is sent to Biohacks. If you tap “Save on this device”, your answers and result stay in your browser only, so you can compare next time. You can delete them whenever you like.

Sources

• Nes et al. (2011): Estimating V̇O₂peak from a nonexercise prediction model: the HUNT Study, Norway, Med Sci Sports Exerc
• Loe et al. (2013): Aerobic capacity reference data in 3816 healthy men and women 20–90 years, PLoS One
• Øvretveit, Klevjer et al. (2025): Polygenic prediction of cardiorespiratory fitness in the Trøndelag health study (HUNT), Sci Rep (activity index)
• Nes et al. (2014): A simple nonexercise model of cardiorespiratory fitness predicts long-term mortality, Med Sci Sports Exerc
• Helgerud et al. (2007): Aerobic high-intensity intervals improve VO₂max more than moderate training, Med Sci Sports Exerc
• WHO (2020): Guidelines on physical activity and sedentary behaviour
• WHO: Healthy diet (fact sheet)
• Hirshkowitz et al. (2015): National Sleep Foundation's sleep time duration recommendations, Sleep Health

The test gives an estimate based on a formula and averages from large studies, and it does not replace an assessment by a doctor. Your answers are calculated in your browser and are not sent to us. If you choose to save your result, it stays on this device only.