VO2 Max Calculator

How this VO2 max calculator works

VO2 max is the most oxygen your body can use during hard exercise, in milliliters per kilogram of body weight per minute (ml/kg/min). Higher means fitter. Apple Watch calls it Cardio Fitness.

This calculator compares yours with the FRIEND registry's reference standards, updated in 2022. It uses the treadmill standards: 16,278 lab tests of apparently healthy US adults aged 20 to 89, without diagnosed cardiovascular disease or COPD. You get two numbers:

• Your percentile: where you rank among people of your sex in your decade of age, such as 30 to 39. At the 50th percentile, half of them score higher. FRIEND publishes every 10th percentile, and the calculator draws a straight line between them. Past the 90th or below the 10th, it says so instead of guessing.
• Your fitness age: the age at which your VO2 max would be the median for your sex.

For example, a 38-year-old man with a VO2 max of 46 ranks in the 69th percentile for his age group and has a fitness age of 26.

VO2 max chart by age

VO2 max in ml/kg/min at five percentiles for each decade, from the 2022 FRIEND treadmill standards. The 50th percentile is the median. Enter your own number above for your exact percentile.

Men

Women

The median falls with every decade, by about 13.5% per decade on average, or 4 ml/kg/min. Men score higher at every age. That's why the calculator compares you only with people of your own age and sex.

What is a good VO2 max?

It depends on your age and sex, so your percentile is the fairest way to judge it. Above the 50th percentile, you beat half of people like you. For ages 40 to 49, that's above 35.3 ml/kg/min for men and 25.7 for women.

Higher keeps paying off. A Cleveland Clinic study followed 122,007 adults for a median of 8.4 years after a treadmill test, and ranked each one against people of the same age and sex:

• Risk of death fell with every step up in fitness, with no upper limit seen.
• The least fit quarter had 5 times the risk of the fittest 2.3%.
• Below average fitness (25th to 49th percentile) carried 41% more risk than above average (50th to 74th), the same increase the study found for smoking.

A meta-analysis of 33 studies found that each extra 3.5 ml/kg/min of VO2 max came with 13% lower risk of death from any cause. Both describe large groups, not a promise for one person.

Apple Watch VO2 max (Cardio Fitness)

Apple Watch Series 3 or later estimates your VO2 max from your heart rate and movement during Outdoor Walk, Outdoor Run, and Hiking workouts in the Workout app. It also uses your age, sex, weight, height, and any medications that limit your heart rate, from the Health app. Indoor workouts don't count. Your first estimate can take at least a day of wearing the watch, then several of those workouts.

To find yours, open the Health app, tap Browse, then Heart, then Cardio Fitness. Tap M to see your average for the past month, and enter that above rather than a single reading.

Apple sorts readings into four levels for your age and sex, based on FRIEND data: High, Above Average, Below Average, and Low. Tap Show All Cardio Fitness Levels to see them. Levels start at age 20, and the watch reports values from 14 to 65 ml/kg/min.

Apple Watch can also notify you if your cardio fitness stays low. For ages 20 to 59, Apple's white paper puts the threshold at the lowest fifth for your sex and decade. From 60, it's 18 ml/kg/min for men and 15 for women.

If the Health app finds that your past estimates could be more accurate, Cardio Fitness offers to update your data. Tap Update under Update Your Data, and a notification shows how your estimates changed.

Apple has also announced an at-home assessment that uses the iPhone camera to measure flexibility, strength, balance, movement mechanics, and VO2 max. Apple says its VO2 max test needs Apple Watch, AirPods Pro 3, or a third-party heart rate sensor.

Why Apple's level and your percentile can differ

Apple hasn't published the numbers behind its four levels. Its 2021 white paper cites the 2015 FRIEND standards. This calculator uses the 2022 update, whose treadmill values run 1.5 to 4.6 ml/kg/min lower, so the same reading can rank a little higher here. And a level is one of four broad bands, while a percentile shows where you sit within them.

How accurate is Apple Watch VO2 max?

Close on average, but single readings vary. In Apple's validation study of 221 people, watch estimates averaged 1.4 ml/kg/min above the lab reference, with a standard deviation of 4.7. That reference was projected from heart rate and oxygen readings below max effort, not measured in an all-out test.

Some things throw it off:

• Heart rate medications. Beta blockers and calcium channel blockers can make the estimate too high unless you add them in the Health app.
• Wrong details. An incorrect age, sex, or weight in the Health app can skew every estimate.
• Extra load. A heavy backpack, carrying a child, or walking on sand makes you work harder than the watch can tell, so the estimate can come out low.
• A raised heart rate. Dehydration, caffeine, extreme heat, or a recent move to high altitude can also make it come out low.

For better estimates, do outdoor walks, runs, or hikes often, on fairly flat ground and at an effort that gets your heart rate up, and wear your watch through the day.

The FRIEND charts come from all-out lab tests that measure oxygen directly. Apple Watch estimates it from your heart rate. So treat your percentile as a close guide, not a lab result.

How to improve your VO2 max

Most people can raise their VO2 max by doing cardio harder and more often. In studies, high-intensity interval training gives the biggest gains: programs of 6 to 12 weeks generally raised VO2 max by about 5 to 10%. It drops fast without training, too, by up to 27% after 2 to 3 weeks of inactivity.

Genes are thought to explain 50 to 70% of the differences in VO2 max between people. So compare yourself with your own past numbers, not only with others. The heart rate zone calculator gives you the heart rates for easy and hard sessions.

What is fitness age?

Fitness age turns your VO2 max into an age: the age at which your number would be the median for your sex. The calculator places each decade's median at the middle of the decade, such as 35 for 30 to 39, and draws straight lines between them. A fitness age below your real age means your VO2 max is higher than typical for your age.

Your percentile compares you with your whole decade. Fitness age uses the typical VO2 max at your exact age, so near the start or end of a decade the two can disagree a little. Other fitness age tools use different data and formulas, so expect a different number from each.

Track your VO2 max with Ness

A calculator gives you a snapshot. Ness reads your VO2 max from Apple Health and puts it to work:

• Biological age: VO2 max can move your biological age more than any other factor, by up to 6 years. Ness compares your median over the past 180 days with what's typical for your age and sex, and shows the years it adds or takes off.
• Cardio load: whether your past 7 days of cardio were lighter or heavier than your usual week.
• Heart rate zones: time in each zone for every workout, and over weeks and months.

Ness is an AI health coach for iPhone and Apple Watch. It also scores your sleep, recovery, strain, and stress every day, logs meals from a photo, and answers questions about your own data.

FAQ

What is a good VO2 max? It depends on your age and sex. Above the 50th percentile, you beat half of people like you. For ages 40 to 49, the median is 35.3 ml/kg/min for men and 25.7 for women. Higher is better: in a study of 122,007 adults, risk of death kept falling as fitness rose, with no upper limit seen.

What is the average VO2 max by age? The median VO2 max for men is 46.5 at 20–29, 39.7 at 30–39, 35.3 at 40–49, 29.2 at 50–59, 24.6 at 60–69, 20.6 at 70–79, and 17.6 at 80–89 ml/kg/min. For women, it's 36.6 at 20–29, 28.3 at 30–39, 25.7 at 40–49, 22.9 at 50–59, 19.6 at 60–69, 17.2 at 70–79, and 15.4 at 80–89. These come from lab treadmill tests in the FRIEND registry.

Is 44 a good VO2 max? For most adults, yes. It's above the median for every age group except men aged 20 to 29. For men, 44 ranks in the 41st percentile at 20–29, in the 62nd percentile at 30–39, and in the 77th percentile at 40–49. For women, it ranks in the 77th percentile at 20–29 and above the 90th percentile at 30–39.

How do I calculate my VO2 max? The most accurate way is a lab test: you walk or run on a treadmill, or ride a bike, at rising effort while a mask measures the oxygen you breathe in and out. Apple Watch estimates it from your heart rate during outdoor walks, runs, and hikes. Once you have a number, enter it above to see how it ranks.

Can Apple Watch measure VO2 max? It estimates it. Apple Watch Series 3 or later estimates VO2 max during Outdoor Walk, Outdoor Run, and Hiking workouts, and shows it as Cardio Fitness in the Health app. In Apple's validation study, estimates averaged 1.4 ml/kg/min above the lab reference.

What is a good VO2 max on Apple Watch? The same as any VO2 max, since Apple Watch reports it in ml/kg/min. The Health app shows your level for your age and sex: High, Above Average, Below Average, or Low. For a finer answer, enter your Cardio Fitness number above to see your percentile.

Why is my Apple Watch VO2 max so low? First check that your age, sex, weight, and height are right in the Health app. Readings can also come out low after workouts with a heavy backpack or on sand, or when you're dehydrated, hot, or have had caffeine. Brisk outdoor walks or runs on fairly flat ground give the watch the best data. If it stays low, it may be accurate, and training can raise it.

What happens if my cardio fitness is low on Apple Watch? Apple Watch can notify you when your cardio fitness stays low for your age and sex, and again if it remains low. Apple says most people can improve their VO2 max by making cardio harder and more frequent, and suggests talking with your doctor about it.

How can I increase my VO2 max quickly? High-intensity interval training works best in studies. Programs of 6 to 12 weeks generally raised VO2 max by about 5 to 10%. Keep it up: VO2 max can drop by up to 27% after 2 to 3 weeks of inactivity.

What is fitness age? The age at which your VO2 max would be the median for your sex. A fitness age below your real age means your VO2 max is higher than typical for your age. For example, a VO2 max of 40 gives men a fitness age of 35 and women a fitness age of 21.

Does VO2 max decrease with age? Yes. In the FRIEND registry, the median fell by about 13.5% per decade, or 4 ml/kg/min, across six decades. That's why the calculator compares you only with people your own age.

Does this calculator save my data? It runs in your browser and sends nothing anywhere. It remembers your entries on this device so you can check again after your next workout. Delete them from the fields anytime.

Related reading

• Biological Age Calculator
• HRV by Age Calculator
• Heart Rate Zone Calculator
• Heart Rate Zones on Apple Watch: How to Set Them and Train With Them
• Apple Health Age: What It Is and How It Compares to Biological Age Apps

Sources

1. Kaminsky LA, et al. Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing: Data from the Fitness Registry and the Importance of Exercise National Database (FRIEND). Mayo Clinic Proceedings, 2022.
2. Kaminsky LA, Arena R, Myers J. Reference Standards for Cardiorespiratory Fitness Measured With Cardiopulmonary Exercise Testing: Data From the Fitness Registry and the Importance of Exercise National Database. Mayo Clinic Proceedings, 2015.
3. Mandsager K, et al. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open, 2018.
4. Kodama S, et al. Cardiorespiratory Fitness as a Quantitative Predictor of All-Cause Mortality and Cardiovascular Events in Healthy Men and Women. JAMA, 2009.
5. Apple. Using Apple Watch to Estimate Cardio Fitness with VO2 max. 2021.
6. Apple Support. Track your cardio fitness levels.
7. Apple Newsroom. Cardio fitness notifications are available today on Apple Watch. 2020.
8. Apple Newsroom. Apple advances health and fitness capabilities using Apple Intelligence and the most accurate heart rate sensing in a wearable. 2026.

This calculator is for general wellness and education. It isn't medical advice. Talk to your doctor before starting hard exercise if you have a heart condition or other health concerns.