Apple Watch VO2 max: is your Cardio Fitness good for your age?
Enter the Cardio Fitness number from your Apple Watch. See how it ranks against lab tests for your age and sex, after allowing for the watch reading low.
Add your details to see where you stand.
Apple Watch Cardio Fitness by age, in ml/kg/min
| Age | 25th | 50th | 75th | 90th |
|---|---|---|---|---|
| 20 to 29 | 26.4 | 33.3 | 39.4 | 44.5 |
| 30 to 39 | 21 | 25.7 | 32.1 | 38.3 |
| 40 to 49 | 18.9 | 23.4 | 28.6 | 34.4 |
| 50 to 59 | 17.5 | 20.8 | 24.9 | 29.5 |
| 60 to 69 | 14.7 | 17.8 | 21.2 | 24.8 |
| 70 to 79 | 13.3 | 15.6 | 18.4 | 20.7 |
| Age | 25th | 50th | 75th | 90th |
|---|---|---|---|---|
| 20 to 29 | 34.2 | 42.3 | 48.4 | 53.3 |
| 30 to 39 | 28.8 | 36.1 | 43.8 | 50.5 |
| 40 to 49 | 25.6 | 32.1 | 39.1 | 46.2 |
| 50 to 59 | 21.2 | 26.5 | 33 | 39.5 |
| 60 to 69 | 17.8 | 22.4 | 27.6 | 33.7 |
| 70 to 79 | 15.1 | 18.7 | 22.6 | 26.7 |
Apple Watch Cardio Fitness, in ml/kg/min, at each percentile of lab treadmill tests, after allowing for the watch reading about 10% low. FRIEND registry treadmill tests, Kaminsky et al., Mayo Clinic Proceedings, 2022.
Is Apple Watch VO2 max accurate?
It's a fair estimate that runs low. In a 2025 study of 28 mostly fit adults, Apple Watch came in about 6 ml/kg/min under a lab treadmill test. A 2024 study of Series 7 found it 4.5 under a bike test, with the gap largest in the fittest people and reversed in the least fit.
How this calculator allows for it
Before comparing your number with lab tests, it adds 10%, the same as the Ageon app. That adds about 4 to a reading of 40 and 2.5 to a reading of 25, so it closes most of the gap where the gap is large and stays small where the watch may already read high.
The table works the other way: it shows what your watch would read at each lab percentile. Fitness age is a prediction: the age at which your result would be exactly average for your sex. It isn't a medical measure, but it turns a percentile into something easier to feel.
How to get a reading
Apple Watch estimates Cardio Fitness during outdoor walks, runs and hikes on fairly flat ground, once your heart rate rises enough. A brisk outdoor walk or run of 20 minutes or more, a few times a week, keeps it up to date. Without a watch, estimate it from a race time on the VO2 max calculator.
Why it matters
Cardio fitness is one of the strongest predictors of how long you'll live. Among 122,007 people who took a treadmill test, the least fit quarter for their age were five times as likely to die over about 8 years as the fittest 2%.
Questions
What is a good Cardio Fitness on Apple Watch?
For a 40-year-old man, a reading around 34 is average and above 41 is good. For a 40-year-old woman, around 25 is average and above 30 is good. The table on this page shows each decade.
Why is my Apple Watch VO2 max lower than my lab test?
The watch estimates it from your heart rate and pace on walks and runs, while a lab measures the oxygen you use at your limit. Studies find the watch reads a few points low on average, and more in fit people.
How can I raise my Cardio Fitness?
Two or three steady cardio sessions a week plus one harder one. In trials with healthy adults under 45, a few months of training raised VO2 max by about 5 ml/kg/min.
Sources
- Investigating the accuracy of Apple Watch VO2 max measurements: a validation study. Lambe et al., PLoS One, 2025.
- Assessing the accuracy of smartwatch-based estimation of maximum oxygen uptake using the Apple Watch Series 7: validation study. Caserman et al., JMIR Biomedical Engineering, 2024.
- Updated reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing. Kaminsky et al., Mayo Clinic Proceedings, 2022.
- Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. Mandsager et al., JAMA Network Open, 2018.
Go deeper: Why VO2 max tracks how well you're aging