Metric
VO2 Max
What counts as a good VO2 max for your age, how much to trust your watch's estimate, and why it matters.
VO2 max is the closest thing a wearable gives you to a single fitness number, and it's one of the more researched metrics for long-term health. Your watch only estimates it, with varying accuracy. Here's what's normal for your age, how the estimate is made, and what the research connects it to.
What your device actually calls this
Scientific measurementMaximal oxygen uptake during exercise, in ml/kg/min. The lab gold standard requires a supervised treadmill/bike test with expired-gas analysis, which no consumer wearable does.
| Device | What they call it | What it actually measures |
|---|---|---|
| Apple Watch | "Cardio Fitness" (a branded name, not the scientific term) | Estimated from walking/running heart rate data, per Apple's own published technical paper. Classified into four tiers (Low/Below Average/Above Average/High), not a raw number by default. |
| Garmin | "VO2 Max" (keeps the scientific term directly) | Firstbeat Analytics algorithm, analyzing the heart rate-to-pace relationship during outdoor runs/walks. |
| Fitbit | "Cardio Fitness Score" | Tracks the relationship between running pace and heart rate during a run, compares that against resting heart rate, then benchmarks the result against age, sex, and weight norms. |
| RingConn | "VO2 Max" | Added via a 2025 app update, estimated from heart-rate response during a run or walk plus age, weight, and gender. |
| Ultrahuman Ring | "VO2 Max" | Calculated from age, gender, mobility level, max heart rate, resting heart rate, and body weight, an inputs-and-formula approach rather than a dedicated test. |
| Coros | "Fitness Level" | Estimated via Coros's own EvoLab engine rather than the licensed Firstbeat algorithm Garmin uses. Methodology is unpublished; no independent validation was found. |
| Polar Vantage | "Polar Fitness Test" | Estimated at rest from heart rate, no exercise required. A 2025 study against CPET found 13.7% mean absolute error, but accuracy varies sharply by population: 23.8% overestimate in a healthy group, 102.4% in a Fontan-circulation group. |
Apple deliberately renamed this to "Cardio Fitness" rather than using the technical term, and Fitbit uses the near-identical branded name "Cardio Fitness Score" for its own separate estimate, a genuine naming coincidence between two unrelated brands rather than a shared methodology. "Cardio Fitness" on an iPhone/Watch, "Cardio Fitness Score" on a Fitbit, and "VO2 Max" on a Garmin are all the same underlying concept, so someone comparing devices might not realize all three are estimating the same thing. Oura and Whoop don't offer a standalone VO2 max estimate of any kind.
Device measurement accuracy: Emerging · on the Research DeskHow each device actually shows this
Apple Watch
"Cardio Fitness" (a branded name, not the scientific term)
Garmin
"VO2 Max" (keeps the scientific term directly)
Fitbit
"Cardio Fitness Score"
RingConn
"VO2 Max"
Ultrahuman Ring
"VO2 Max"
Coros
"Fitness Level"
Polar Vantage
"Polar Fitness Test"
See every device →
Sources: Apple's own technical PDF, "Using Apple Watch to Estimate Cardio Fitness with VO2 max" (apple.com), a genuine primary source. Garmin's Firstbeat detail from Garmin's own technology page (garmin.com). Fitbit/Google's own support documentation (official); Freeberg KA et al., "Assessing the ability of the Fitbit Charge 2 to accurately predict VO2max," mHealth, 2019, doi:10.21037/mhealth.2019.09.07.
The benchmark
VO2 Max
VO2 Max by Age: What's Considered Good?
Where your number sits by age, and how far to trust your watch's estimate.
See how you compareExample result
Man · 50 · 38
about the 69th percentile, Good for your age
ACSM data, 80,000+ adults
More on VO2 Max
What Is VO2 Max, and Why Does It Matter?
VO2 max is among the strongest predictors of all-cause mortality in healthy adults. The number your watch displays is a different kind of estimate entirely.
Watch VO2 Max Missed the Lab Number by 7% to 16%
Watch VO2 max missed the lab measurement by 7% to 16% in three tests. Estimated fitness still predicts death risk much like measured fitness.
VO2 Max and Longevity: A Consistent, Graded Relationship
Fitness measured by direct exercise testing tracks mortality risk in a consistent graded pattern, across dozens of pooled analyses and across decades.
How Consumer Wearables Model VO2 Max From Heart Rate and Pace
Your watch never analyses your breath. It models heart rate against pace or power and maps that onto a population-derived oxygen scale, with its own error.
Can Medication Improve VO2 Max Without Exercise?
No medication in this research has been shown to raise VO2 max on its own. The most direct test improved blood sugar without a matching change in fitness.
Fitness vs Weight: What the Mortality Research Actually Shows
Research on fitness and weight finds cardio fitness predicts mortality risk more strongly than weight category in healthy adults, not in heart patients.
Do Short Bursts of Exercise Actually Raise Your VO2 Max?
Stair-climbing bursts spread through the day raised peak oxygen uptake over about six weeks in inactive young adults, measured against doing nothing at all.
Do Fitness Trackers Actually Improve Health Outcomes?
Trackers are linked to more movement and better fitness, and fitness predicts mortality. Those are two separate bodies of evidence, joined here by inference.
Does VO2 Max Protect Against Cognitive Decline?
Higher fitness tracks with slower markers of brain aging and better cognition in older adults. The studies behind that are cross-sectional, so it is a link.
HIIT vs Steady-State Cardio for VO2 Max
A meta-analysis found intervals and steady endurance work both raise VO2 max without settling which wins. The larger interval gain came from cardiac rehab.
Higher VO2 Max Went With Lower Death Risk in Heart Failure
In 64 heart failure studies, each 1 mL/kg/min higher peak VO2 went with 14% lower all-cause death risk (HR 0.86). Heart-specific death: not significant.
Can a Proteomic Test Actually Predict VO2 Max?
A blood protein score tracked with fitness and predicted mortality on its own. That is not the same as a blood draw replacing a treadmill test.
Zone 2's Mitochondria Claim Rests on Elite Athletes, Not You
A 2025 narrative review found Zone 2 training's mitochondrial evidence comes from elite athletes, and argues it does not transfer to lower volumes.
Does the Number of Sprints in a Sprint Interval Workout Actually Matter for VO2max?
Sprint interval training is sold on doing fewer, harder efforts. A 93-trial meta-analysis tested whether more sprints per session actually improves VO2max more.
Does Strength Training Improve VO2max as Much as Cardio?
A pooled analysis of 38 randomized trials in middle-aged and older adults compared aerobic training against resistance training head-to-head for VO2max.
Does Fitness Still Matter Once You've Been Diagnosed With Cancer?
VO2 max gets framed as a prevention number. A 42-study meta-analysis in cancer patients shows fitness keeps mattering well after diagnosis too.
Your Watch's VO2 Max Is a Formula. Does Estimated Fitness Still Predict Lifespan?
VO2 max's longevity link comes from treadmill tests. Research on formula-based estimates, and a real check on Apple Watch's own number, complicate that.
Why Your Estimated VO2 Max Might Drop Without Your Fitness Actually Changing
A validation study of Apple Watch VO2max against lab gas analysis found 15.79 percent mean absolute error and reliability rated poor at ICC 0.47.
Does Ozempic Improve Your Fitness?
In 193 adults, cardiorespiratory fitness improved only when structured exercise was added, not from the drug alone. VO2 max is reported per kilogram, so the number rises anyway.
What Is a Good VO2 Max for a 40 Year Old?
In your 40s the median VO2 max is 37.8 ml/kg/min for men and 26.7 for women. The full 5th to 95th percentile ladder, and how far a watch estimate can move you on it.
What Is a Good VO2 Max for a 50 Year Old?
In your 50s the median VO2 max is 32.6 ml/kg/min for men and 23.4 for women. The full percentile ladder, why reference values may understate women, and what a watch can do to your row.
What Is a Good VO2 Max for a 60 Year Old?
In your 60s the median VO2 max is 28.2 ml/kg/min for men and 20.0 for women. The full percentile ladder, what training does at this age, and how much a watch reading can drift.
What Is a Good VO2 Max for a 70 Year Old?
In your 70s the median VO2 max is 24.4 ml/kg/min for men and 18.3 for women. In 1,565 Norwegians aged 70 to 77, readings below 26.5 for men and 22.2 for women went with higher mortality.
What's the Difference Between VO2 Max and VO2 Peak?
VO2 max is the oxygen ceiling confirmed by a plateau; VO2 peak is the highest value a test reached, plateau or not. Why they usually match in a full-effort test, when they may not, and which one the age tables actually report.