What is VO2 max?
VO2 max is the maximum amount of oxygen your body can take in and use during all-out exercise, measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It is widely considered the single best snapshot of aerobic, or cardiovascular, fitness. The higher the number, the more oxygen your heart, lungs and muscles can move and burn, and the longer you can sustain hard effort before fatigue sets in.
The gold-standard measurement is a lab test on a treadmill or bike with a mask that captures every breath. That is accurate but expensive and rarely accessible, so most people rely on field-test estimates instead. VO2 max also matters beyond athletics: large studies link higher cardio fitness to lower risk of heart disease and longer life expectancy, which is why wearables like Apple Watch now track it for everyday users.
What is a good VO2 max by age?
There is no universal "good" number, because VO2 max naturally declines with age and differs between men and women. A reading that is excellent for a 55-year-old would be merely fair for a 25-year-old. The table below shows widely published norms, in ml/kg/min, used to sort estimates into six categories from very poor to superior. Find your age band and sex, then see where your calculated number lands.
| Men | Very poor | Poor | Fair | Good | Excellent | Superior |
|---|---|---|---|---|---|---|
| 20–29 | <33 | 33–36 | 37–41 | 42–48 | 49–52 | 53+ |
| 30–39 | <31 | 31–34 | 35–40 | 41–46 | 47–50 | 51+ |
| 40–49 | <30 | 30–32 | 33–38 | 39–44 | 45–48 | 49+ |
| 50–59 | <26 | 26–30 | 31–35 | 36–41 | 42–45 | 46+ |
| 60+ | <20 | 20–25 | 26–31 | 32–36 | 37–44 | 45+ |
| Women | Very poor | Poor | Fair | Good | Excellent | Superior |
|---|---|---|---|---|---|---|
| 20–29 | <28 | 28–30 | 31–34 | 35–40 | 41–44 | 45+ |
| 30–39 | <27 | 27–29 | 30–33 | 34–38 | 39–42 | 43+ |
| 40–49 | <25 | 25–27 | 28–30 | 31–35 | 36–40 | 41+ |
| 50–59 | <21 | 21–23 | 24–27 | 28–32 | 33–36 | 37+ |
| 60+ | <19 | 19–21 | 22–23 | 24–29 | 30–33 | 34+ |
If you are under 20, the calculator applies the 20–29 band as the closest reference; treat that result as a loose guide, since published norms for adults do not map cleanly onto teenagers.
How to calculate VO2 max without a lab
Three field tests let you estimate VO2 max at home or at a local track. Each one trades a little accuracy for convenience, and the calculator above runs all three.
Resting heart rate estimate (Uth–Sørensen)
This is the quickest method and needs no exercise at all. It uses the formula VO2max = 15.3 × (maximum heart rate ÷ resting heart rate), where maximum heart rate is estimated as 220 minus your age. Because a fitter heart pumps more blood per beat, a lower resting heart rate produces a higher estimate. It is convenient but the least precise of the three, since it leans entirely on heart-rate ratios rather than measured effort.
Cooper 12-minute run test
Developed for the military, the Cooper test asks you to cover as much ground as possible in 12 minutes of running on a flat course, then plugs the distance in metres into VO2max = (distance − 504.9) ÷ 44.73. It is more accurate than the resting-heart-rate method because it reflects real maximal effort, but it demands a hard all-out run, which is not suitable for everyone.
Rockport 1-mile walk test
The Rockport test is a gentler alternative built around walking one mile as briskly as you can, then recording your time and your heart rate at the finish. It folds in sex, age, weight, walk time and finishing heart rate, which makes it a strong choice for people who are not comfortable running. Its accuracy depends on walking at a genuinely brisk, steady pace and on a reliable heart-rate reading at the line.
How Apple Watch estimates VO2 max (Cardio Fitness)
Apple Watch reports VO2 max under the label "Cardio Fitness" in the Health app. Rather than asking for a treadmill test, it estimates the number in the background from your heart rate and motion during outdoor walks, runs and hikes, where it can pair effort with GPS-tracked speed and incline. The more outdoor cardio sessions you log, the more data it has to refine the estimate.
Apple Watch also classifies your Cardio Fitness as high, above average, average, below average, or low for your age and sex, and it can send a notification when your level reads low or below average. Those alerts are designed as a prompt to pay attention to aerobic fitness, not as a diagnosis. The trend over time is more meaningful than any single reading.
How to improve your VO2 max
VO2 max responds to training, and most people can raise it with a consistent routine that mixes two intensities:
- Zone 2 base work. Easy, conversational cardio — a pace where you can still talk in full sentences — for 30 to 60 minutes builds the aerobic foundation that supports a higher ceiling. Most weekly cardio should sit here.
- Intervals. One or two sessions a week of harder efforts near your maximum, alternated with recovery (for example, repeated 3- to 4-minute hard pushes), are the most direct stimulus for lifting VO2 max.
Progress comes from weeks and months of consistency rather than any single workout, and recovery between hard sessions is part of the process. Re-testing every few weeks with the same method shows whether the trend is moving in the right direction.
Your cardio fitness, in one daily score
Health Genie reads your Apple Watch steps and resting heart rate and turns them into one clear Vitality Score each morning — a private, plain-English read on how your body is doing, with no dashboards to decode.
Download Health Genie FreeFrequently asked questions
What is a good VO2 max for my age?
A good VO2 max depends on your age and sex, because cardio fitness naturally declines with age. As a rough guide, a man in his 20s reaches the "good" band from about 42 ml/kg/min, while a woman in her 20s reaches it from about 35, and both thresholds fall by roughly 3 to 5 points each decade. Use the calculator above to see which fitness category your estimate lands in for your exact age and sex.
How do I calculate my VO2 max?
You can estimate VO2 max without a lab using one of three field tests. The resting heart rate method uses 15.3 multiplied by your maximum heart rate divided by your resting heart rate; the Cooper test uses the distance covered in a 12-minute run; and the Rockport test uses your time and finishing heart rate after walking one mile. Each method trades some accuracy for convenience, and the calculator above runs all three.
Is a VO2 max of 50 good?
A VO2 max of 50 ml/kg/min is good to excellent for most adults. For a man under 40 it sits in the excellent range, and for a woman of almost any age it is excellent or superior. Values around 50 reflect a well-conditioned cardiovascular system, but checking the category table for your specific age and sex shows exactly where it falls.
How can I improve my VO2 max?
VO2 max improves with regular aerobic training that challenges the heart and lungs. A common approach combines a base of easy Zone 2 cardio with one or two weekly interval sessions, alternating hard efforts near your maximum with recovery. Consistency over weeks and months matters more than any single workout, and most people can raise their VO2 max with steady training.
How does Apple Watch estimate VO2 max?
Apple Watch labels VO2 max as "Cardio Fitness" and estimates it automatically from your heart rate during outdoor walks, runs and hikes, with no treadmill or mask test required. Over time it can send a notification if your cardio fitness reads low or below average for your age and sex. The estimate updates as you record more outdoor cardio sessions.
How accurate is Apple Watch VO2 max?
Apple Watch VO2 max is an estimate, not a lab measurement, so individual readings can differ from a clinical test by several points. Its real strength is tracking the trend over weeks and months rather than any single number. For most people it is accurate enough to show whether cardio fitness is improving, holding steady, or slipping.