Heart & circulation
What Counts as a Good VO2 Max for Your Age and Sex?
Search 'VO2 max chart' and the number for the same age and sex can differ by ten points depending which chart you land on — because a lab gas-exchange test, a submaximal prediction and a wearable's algorithm are three different measurements wearing the same name.
The short answer
There is no single number that counts as a good VO2 max: what counts is how your value compares with people of your own age and sex, because oxygen uptake falls across the decades and men typically post higher raw figures than women throughout adulthood. The American Heart Association's clinical framework ranks fitness by age- and sex-matched percentile rather than one universal cut-off, and treats a falling trend in your own number, tracked over time, as more informative than any chart's rating of a single test.
What this actually measures
VO2 max measures the maximum rate at which your body can take in, transport and use oxygen during exertion, expressed in millilitres of oxygen per kilogram of bodyweight per minute (mL/kg/min) or in metabolic equivalents (METs). It's a whole-system figure — how much blood the heart pumps per beat, how much oxygen the blood carries, and how efficiently muscle extracts and burns that oxygen — not a reading on any single organ.
| Band | Value | What it depends on |
|---|---|---|
| Maximal lab test (gas exchange) | Oxygen uptake measured directly, breath by breath, during a supervised maximal treadmill or cycle-ergometer effort | The reference-standard method, and the one age- and sex-matched percentile tables are actually built from |
| Submaximal or non-exercise estimate | Predicted from your heart-rate response to a lighter workload, or from age, resting heart rate, activity level and body measurements alone | What most clinic and consumer results actually are; accuracy depends entirely on the prediction equation used, which most reports don't name |
| Population percentile (age- and sex-matched) | Where a measured or estimated value ranks against others of the same age and sex, rather than one fixed universal threshold | The approach the American Heart Association's 2016 statement recommends for clinical use, built from a national exercise-testing registry |
Why the charts don’t agree
Search “VO2 max by age” and open the first five results. The figure for a 45-year-old man rarely matches across them — sometimes by ten points on the same mL/kg/min scale. That’s not because exercise science can’t settle on a fact. It’s because the charts are measuring different things and calling them the same thing.
A VO2 max number can come from a supervised maximal treadmill test with breath-by-breath gas analysis, a submaximal test that extrapolates from a lighter effort, a formula built from your age and resting heart rate with no exercise at all, or a wearable’s proprietary algorithm reading your heart rate and motion. Each produces a number. None of them is exactly wrong — they’re answering slightly different questions — but a chart that doesn’t say which method it used isn’t reporting a fact. It’s reporting an average of several loosely related things and presenting it as one.
What the number is actually measuring
VO2 max is the maximum rate at which your body can take in, transport and use oxygen during exertion, expressed in millilitres of oxygen per kilogram of bodyweight per minute. It’s a whole-system figure: how much blood your heart pumps per beat, how much oxygen your blood carries, and how efficiently your muscles extract and burn that oxygen once it arrives. A weak link anywhere in that chain lowers the ceiling, which is exactly why it’s a useful summary measurement and a poor diagnostic one — a low score tells you something in the chain is limiting you, not which link it is.
Because the figure is expressed per kilogram, two changes that have nothing to do with your heart or lungs can move it. Losing fat mass raises your VO2 max arithmetically even if your cardiovascular fitness hasn’t changed at all, and gaining muscle without a matching rise in oxygen delivery can lower it the same way. Worth knowing before you read too much into a month-to-month change on any device.
The approach the American Heart Association actually recommends
In 2016 the American Heart Association published a scientific statement arguing that cardiorespiratory fitness should be assessed in clinical practice as a vital sign, alongside blood pressure and resting heart rate, because low cardiorespiratory fitness is associated with a high risk of cardiovascular disease, all-cause mortality, and mortality from several cancers.
The framework it lays out isn’t a single “good” number. It’s a percentile ranking — where a measured or estimated VO2 max sits against a large registry of other people of the same age and sex, rather than against one fixed threshold that’s supposed to apply equally to a 25-year-old and a 65-year-old. That’s the more defensible version of “good”: not a number you clear once, but a rank that shifts as you and your peer group age together.
It’s also why a single chart claiming to show the good VO2 max for every 40-year-old is doing something the underlying science doesn’t really support. It’s collapsing a whole distribution of people into one number and presenting the collapse as a fact.
| Measurement method | What it actually captures | Where it falls short |
|---|---|---|
| Maximal lab test (gas exchange) | Oxygen uptake measured directly during a supervised maximal effort | The reference standard, but needs equipment, supervision and a true maximal effort almost nobody attempts casually |
| Submaximal test | Oxygen uptake predicted from your heart-rate response to a lighter, safer workload | Accuracy depends on the prediction equation and how close your real maximum heart rate is to the one it assumes |
| Non-exercise estimate | Predicted from age, resting heart rate, activity level and body measurements, with no test at all | The furthest from a measurement of the four — a statistical guess reported as if it were a result |
| Wearable estimate | A proprietary model built from heart-rate and motion data during ordinary workouts | Useful as a personal trend line; not built to be compared against someone else’s device or a lab figure |
Why men typically score higher than women at the same age
This gap shows up in essentially every dataset on the topic, and it isn’t primarily a story about training effort. Men typically have a larger stroke volume — more blood pumped with each heartbeat — and a higher haemoglobin concentration, meaning each litre of blood carries more oxygen to working muscle. Because VO2 max is conventionally expressed per kilogram of bodyweight, a higher average proportion of body fat to lean tissue in women lowers the per-kilogram figure further, independent of how cardiovascularly fit either person actually is.
None of that makes comparison across sexes meaningless, but it does make a single unisex chart actively misleading. A woman scored against norms built mostly from men’s data will look less fit than she is, for reasons that have nothing to do with her heart or lungs. It’s exactly why age- and sex-specific percentile tables exist rather than one line for everyone.
What happens to the number as you get older
Maximum oxygen uptake declines across adulthood, and the mechanism behind that is reasonably well understood: maximum heart rate falls with age, and maximum stroke volume tends to fall alongside it, so the ceiling on how much oxygenated blood the heart can deliver per minute drops before anything necessarily changes in the muscles themselves.
Staying aerobically active doesn’t cancel that trajectory — nobody’s maximum heart rate climbs back up with training — but a cardiovascular system that keeps being asked to work near its limit tends to sit higher on the same downward curve than one that never is. That’s the practical argument for tracking your own number over years rather than chasing a chart’s verdict on a single test: the trend is the part you can actually act on, and it’s a genuinely different question from where you land on somebody else’s scale this month.
What a wearable’s “fitness age” is actually telling you
“Fitness age” is a repackaging of the same estimated VO2 max, translated into whichever age that score is typical for, rather than expressed as a percentile. If your estimate matches what’s usual for a 30-year-old, the device tells you your fitness age is 30, whatever your actual age is. It’s the identical number wearing a more motivating unit.
That reframing isn’t dishonest, but it inherits the same limitation as the figure underneath it: it comes from a proprietary model reading heart rate and movement, not from measured oxygen uptake, and it will disagree with a lab test and with a different brand’s estimate for the same reason two thermometers can disagree on the same forehead — different instrument, same person. Watch the direction of your own number over months of broadly similar training. Don’t expect the absolute figure to match anyone else’s device, or your own doctor’s lab-measured value, because it isn’t built to.
Where reading this stops being enough
None of the above should be weighed against symptoms during exertion. Chest pain or pressure, dizziness or near-fainting with exercise, breathlessness that’s out of proportion to the effort you’re making, or a sudden and unexplained drop in the exercise you could previously manage are reasons to see a clinician before your next workout — not reasons to retest your VO2 max or check what a chart says is normal for your age.
And if you already have a diagnosed heart condition, or a clinician has advised against unsupervised vigorous exertion, a maximal-effort test belongs in a supervised clinical exercise-testing setting, not attempted alone against a stopwatch to settle where you rank. The framework above is about how to interpret a number once you have one safely. It has nothing useful to say about whether generating that number yourself, today, is the right call — that’s a different, more important question, and it isn’t this article’s to answer.
When to stop reading and see someone
A VO2 max or fitness test is not the place to investigate chest pain or pressure, dizziness or near-fainting during exercise, breathlessness that's out of proportion to the effort involved, or a sudden and unexplained drop in exercise tolerance — those are reasons to see a clinician before your next workout, not reasons to retest your score. A maximal effort test also does not belong outside a supervised clinical exercise-testing setting if you have a diagnosed heart condition or a clinician has already advised against unsupervised vigorous exertion.
Questions we get
What is a good VO2 max score?
There is no single number that counts as good for everyone, because what matters is how your value compares with people of the same age and sex rather than against a fixed universal target. Someone who ranks in the upper range for a 60-year-old woman and someone who ranks the same way for a 25-year-old man are doing equally well relative to their own peer group despite having very different raw mL/kg/min figures. That relative framing, not any single chart number, is the basis the American Heart Association recommends for interpreting cardiorespiratory fitness in its 2016 clinical statement.
Why do VO2 max charts online disagree with each other?
Because they're often built from different measurement methods labelled with the same name. A true VO2 max comes from a supervised maximal exercise test with breath-by-breath gas analysis in a lab; a submaximal test extrapolates from your heart-rate response to a lighter workload; a non-exercise estimate uses your age, resting heart rate, activity level and body measurements with no exercise test at all; and a wearable device runs its own proprietary model from heart-rate and motion data. Each method can return a meaningfully different number for the same person on the same day, so a chart is only as trustworthy as the method behind it — and most charts circulating online don't say which one they used.
Why is VO2 max usually higher in men than in women at the same age?
Mostly for structural and physiological reasons rather than a training gap. Men typically have a larger stroke volume — more blood pumped per heartbeat — and a higher haemoglobin concentration, meaning each litre of blood carries more oxygen. Because VO2 max is conventionally expressed per kilogram of bodyweight, a higher average proportion of body fat to lean mass in women also lowers the per-kilogram figure independent of cardiovascular fitness itself. None of this makes the sexes impossible to compare — it means the comparison has to be made within sex, which is exactly what age- and sex-specific percentile norms exist to do.
Does VO2 max really decline with age, and can training slow it?
Maximum oxygen uptake follows a well-documented downward path across adulthood, driven mainly by a falling maximum heart rate and a declining maximum stroke volume rather than any single cause. Staying aerobically active doesn't reverse that trajectory — maximum heart rate doesn't rise again with training — but a cardiovascular system that keeps being asked to work near its limit tends to sit higher on the same downward curve than one that doesn't. That's one reason the American Heart Association frames cardiorespiratory fitness as a modifiable vital sign worth tracking over years, rather than a fixed trait you either have or don't.
Can I trust a wearable device's VO2 max or 'fitness age' estimate?
Treat it as a trend indicator rather than a diagnostic number. A consumer device estimates VO2 max from heart-rate and motion data using its own proprietary model rather than measuring oxygen uptake directly, so the absolute figure can diverge from a lab-tested value by a meaningful margin. 'Fitness age' is the same estimate translated into the age a score is typical for, rather than expressed as a percentile — it's a more motivating unit wrapped around an identical limitation. What the estimate is genuinely useful for is direction: if the number from the same device, worn the same way, moves steadily over months of similar training, that trend reflects a real change even when the absolute figure wouldn't match a laboratory test.
Where the figures came from
- American Heart Association — Scientific Statement, 'Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign' (Circulation, 2016) — The American Heart Association's 2016 scientific statement recommends assessing cardiorespiratory fitness in clinical practice and states that low cardiorespiratory fitness is associated with a high risk of cardiovascular disease, all-cause mortality, and mortality from various cancers
- Centers for Disease Control and Prevention — Physical Activity Guidelines for Adults — Adults are recommended to get 150 minutes of moderate-intensity aerobic activity a week, or 75 minutes of vigorous-intensity activity, or an equivalent combination of both
- MedlinePlus — Exercise and Physical Fitness — Aerobic ('cardio') exercise such as walking, running or swimming is described as supporting heart, lung and circulatory-system health
Dev Petrossian
Contributor, heart and circulation
Dev writes the heart and circulation entries: blood pressure, cholesterol, resting heart rate. He treats these as measurement problems first — what the device is doing, what the number is sensitive to, and how much of an apparent change is real rather than noise. He is not a clinician and holds no medical qualification; the guideline thresholds in his entries are attributed to the body that published them.
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