How old is your body, really? Estimate your VO2 max and fitness age in a minute, without any exercise test.
Answer six questions. Measure your waist at the belly button, relaxed, after breathing out.
An estimate for training, not a medical diagnosis. Talk to your doctor before starting hard exercise if you have a heart condition, high blood pressure, take heart medication, or have symptoms when you exert yourself.
Fitness age comes from the Cardiac Exercise Research Group at NTNU in Trondheim, the team of Ulrik Wisløff and colleagues that also developed and tested the Norwegian 4x4 protocol. Using the HUNT Study, one of the world's largest health surveys, they measured VO2 max on a treadmill in thousands of healthy adults and found that five simple questions predict it surprisingly well.
Step 1: estimate VO2 max with the sex-specific HUNT model (Nes et al., 2011):
Men: 100.27 − 0.296 × age − 0.369 × waist(cm) − 0.155 × resting HR + 0.226 × PA indexWomen: 74.736 − 0.247 × age − 0.259 × waist(cm) − 0.114 × resting HR + 0.198 × PA indexThe physical-activity (PA) index multiplies the scores of your three exercise answers: frequency (0, 0, 1, 2.5 or 5) × intensity (1, 2 or 3) × duration (0.1, 0.38, 0.75 or 1). It runs from 0 for no exercise to 15 for near-exhausting sessions over an hour, almost every day.
Step 2: find your fitness age. Your estimate is compared with the average treadmill VO2 max of healthy Norwegians in each age group (HUNT 3 Fitness Study):
| Age | Men (ml/kg/min) | Women (ml/kg/min) |
|---|---|---|
| 20–29 | 54.4 ± 8.4 | 43.0 ± 7.7 |
| 30–39 | 49.1 ± 7.5 | 40.0 ± 6.8 |
| 40–49 | 47.2 ± 7.7 | 38.4 ± 6.9 |
| 50–59 | 42.6 ± 7.4 | 34.4 ± 5.7 |
| 60–69 | 39.2 ± 6.7 | 31.1 ± 5.1 |
| 70+ | 35.3 ± 6.5 | 28.3 ± 5.2 |
Values are mean ± standard deviation (Loe et al., 2013). The age where the average equals your estimate is your fitness age. Values between age groups are interpolated.
Once you've done a few weeks of training, measure rather than estimate: the VO2 max calculator uses field tests such as the Cooper run or the Rockport walk.
Fitness age compares your estimated VO2 max with the average for healthy people of your sex. If your fitness matches the average 40-year-old, your fitness age is 40, whatever your real age. The idea comes from NTNU researchers in Trondheim, Norway, the same group that developed the Norwegian 4x4.
First your VO2 max is estimated with the non-exercise model from the HUNT Study (Nes et al., 2011), which uses sex, age, waist, resting heart rate and a physical-activity score. That estimate is then compared with treadmill-tested VO2 max values of healthy Norwegian adults (Loe et al., 2013) to find the age where the average equals yours.
The HUNT model explains about 56–61% of the variation in measured VO2 max, with a typical error of about 5–6 ml/kg/min. That is good for a test without exercise, but it is an estimate. For a more direct number, do a field test with the VO2 max calculator.
In HUNT follow-up data, people whose fitness age was well above their real age had a higher risk of early death (Nes et al., 2014). More broadly, VO2 max is one of the strongest single predictors of long-term health.
Raise your VO2 max and reduce your waist. Hard interval training such as the Norwegian 4x4 moves the activity score most, a lower resting heart rate follows from regular endurance work, and a smaller waist helps directly. This calculator shows how much each change would move your result.
It uses the same published model and HUNT reference data, but it is our own implementation, so results may differ slightly. It is not affiliated with NTNU.