What is a good VO2 max?

What is a good VO2 max?

A good VO2 max sits around the 60th percentile for your age and sex: in Cooper Institute fitness norms, that is roughly 45 mL of oxygen per kilogram per minute for men in their 20s and 30s, and about 39 to 40 for women in the same age range, with the bar dropping as you get older.

VO2 max measures how much oxygen your body can take in and use during maximum effort, expressed in millilitres of oxygen per kilogram of body weight per minute. Exercise physiologists have used it for decades as the default yardstick for cardiovascular fitness. The real test runs in a lab: you walk or run on a treadmill at an increasing pace while breathing through a mask connected to a metabolic cart, until you physically cannot continue. Cleveland Clinic describes this kind of graded exercise test as the field's gold standard. There is no single number that applies to everyone: age, sex and training history all shift where your personal "good" sits.

How VO2 max is measured, and why your watch's number isn't the real one

Almost nobody has access to a metabolic cart, so most people get their VO2 max from a fitness watch instead. These devices infer the number from your heart rate during exercise and your pace, then run it through an algorithm. Cleveland Clinic notes that wearable results are typically close to lab measurements across various studies, and that small week-to-week shifts of 3 to 5 percent in your own number likely reflect ordinary test variability rather than a real fitness change.

A 2024 validation study in JMIR Biomedical Engineering put one popular wearable to a direct test. Researchers compared Apple Watch Series 7 estimates against a real metabolic-cart test in 19 adults on a cycle ergometer. The watch underestimated VO2 max by an average of 4.51 mL/kg/min, with a mean absolute error of about 16 percent and only poor to moderate agreement with the lab reading. The error got worse, not better, for the fittest participants: the watch underestimated their VO2 max by an average of 12 points. If you are already fit and watching the number closely, that is exactly the group the watch is least reliable for.

VO2 max by age and sex: the real numbers

The most widely cited age-and-sex norms come from the Cooper Institute, reprinted across fitness brands including Garmin. For men, a "good" VO2 max runs about 45.4 mL/kg/min in your 20s, 44.0 in your 30s, 42.4 in your 40s, 39.2 in your 50s and 35.5 in your 60s. For women, the same "good" band runs about 39.5 in your 20s, 37.8 in your 30s, 36.3 in your 40s, 33.0 in your 50s and 30.0 in your 60s. "Excellent" and "superior" sit well above those figures at every age, and "poor" sits below the lowest number in each band.

Cleveland Clinic's explanation of the pattern lines up with those figures: VO2 max tends to decline naturally after age 30, dropping roughly 5 to 10 percent per decade, and men average higher scores than women at every age. None of that makes a lower number a verdict on your health. It means the chart you compare yourself against has to match your age and sex, not a 25 year old's.

Why VO2 max matters more than people think

The strongest reason to care about this number comes from a 2018 study in JAMA Network Open that followed 122,007 patients who took a treadmill stress test between 1991 and 2014. Over a median follow-up of 8.4 years, 13,637 of them died. After adjusting for other risk factors, people in the lowest fitness group had more than five times the mortality risk of those in the elite group. People below the average fitness band had a 41 percent higher risk of death than those above it, a bigger gap than the study found for smoking, diabetes or established coronary artery disease.

What makes the study unusual is what happened at the very top. The researchers wrote that there does not appear to be an upper limit of aerobic fitness above which a survival benefit is no longer observed. Even people in the elite fitness bracket had meaningfully lower mortality than those in the merely high bracket. It is an observational study of people referred for a stress test, not a randomised trial of the general population, so it shows a strong association rather than final proof. But it is one of the largest datasets ever assembled on the question.

Can you actually improve it?

Yes, and the type of training seems to matter. A 2014 trial in Frontiers in Physiology put 48 well-trained endurance athletes through nine weeks of one of four training styles: high volume, threshold, high-intensity intervals, or a polarized mix of mostly easy aerobic work with some hard intervals. The polarized group's VO2 max rose by 11.7 percent, from 60.6 to 67.4 mL/kg/min, significantly more than the other three approaches. The all-intervals group improved by 4.8 percent; the threshold-only and high-volume-only groups showed no significant gain.

That trial used athletes who already had a high baseline fitness, so the exact percentages will not transfer to someone starting from a sedentary baseline, who typically sees larger relative gains from almost any structured exercise. The practical lesson still holds: plenty of comfortable, easy-paced aerobic work, the same territory covered in our zone 2 cardio piece, combined with a smaller amount of genuinely hard effort, appears to beat either extreme alone.

What to actually do with your number

If you want a true VO2 max, the only way to get one is a supervised graded exercise test, available at sports science labs, some cardiology clinics and university exercise physiology departments. For almost everyone else, a smartwatch estimate is a reasonable stand-in for tracking direction over time: is the number drifting up or down over months, not what it reads on any single day.

Chasing a specific number is less useful than building the fitness that produces one. The research above points toward a mix of plenty of easy, conversational-pace cardio with a smaller dose of harder intervals, done consistently over months rather than weeks. That is unglamorous advice, but it is what moved the needle in the studies that actually measured it.

Our take

VO2 max is a real, well-studied number with one of the stronger links to mortality risk in exercise science, and that part of the hype holds up. Where the hype runs ahead of the evidence is your watch's specific reading: treat it as a rough trend over months, not a diagnosis, especially once you are already fit. The broader research backs the idea that building aerobic fitness pays off at every level, even where any single device's number should be taken loosely.

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.