A VO2 max at or above the middle of the chart for your age and sex is good: in US lab tests, the median is 39.7 mL/kg/min for men aged 30 to 39 and 28.3 for women the same age. Smartwatch estimates land roughly 13% to 16% away from lab results in independent studies, so read your watch's number as a trend, not a score.
VO2 max is the most oxygen your body can use during all-out exercise, measured in milliliters per kilogram of body weight per minute (mL/kg/min).
How we evaluated this: The ranges come from the FRIEND registry's 2022 reference standards (Mayo Clinic Proceedings). Accuracy figures come from Apple, Garmin and Firstbeat documentation and from peer-reviewed validation studies, all checked Oct 6, 2026. We didn't run lab tests for this article. This page explains what the numbers mean and isn't medical advice. An AI tool helped with research and the first draft, and an editor checked every number against the sources at the bottom.
VO2 max chart by age and sex
These are percentiles from 16,278 treadmill tests with directly measured oxygen uptake, from 34 US labs, in apparently healthy adults (FRIEND registry, 2022). Read it like this: at the 50th percentile, half the people your age and sex scored lower.
Men (mL/kg/min)
|
Age |
20th percentile |
50th (median) |
80th |
90th |
|---|---|---|---|---|
|
20–29 |
35.2 |
46.5 |
54.5 |
58.6 |
|
30–39 |
29.8 |
39.7 |
50.0 |
55.5 |
|
40–49 |
26.7 |
35.3 |
45.2 |
50.8 |
|
50–59 |
22.2 |
29.2 |
38.3 |
43.4 |
|
60–69 |
18.5 |
24.6 |
32.0 |
37.1 |
|
70–79 |
15.9 |
20.6 |
25.9 |
29.4 |
|
80–89 |
14.8 |
17.6 |
21.4 |
22.8 |
Women (mL/kg/min)
|
Age |
20th percentile |
50th (median) |
80th |
90th |
|---|---|---|---|---|
|
20–29 |
27.2 |
36.6 |
44.8 |
49.0 |
|
30–39 |
21.9 |
28.3 |
37.0 |
42.1 |
|
40–49 |
19.7 |
25.7 |
33.0 |
37.8 |
|
50–59 |
18.5 |
22.9 |
28.4 |
32.4 |
|
60–69 |
15.4 |
19.6 |
24.3 |
27.3 |
|
70–79 |
14.0 |
17.2 |
20.8 |
22.8 |
|
80–89 |
12.6 |
15.4 |
18.4 |
20.8 |
Source: Kaminsky et al., Mayo Clinic Proceedings, 2022, Table 3 (treadmill, RER ≥ 1.0).
The study found median VO2 max fell by about 13.5% (4.0 mL/kg/min) per decade on the treadmill. Cycling tests run lower than treadmill tests, so compare a bike-based lab result against cycling norms, not this chart.
Watch labels don't use the same chart
Your watch's word for your score comes from its own reference data:
- Apple Watch sorts you into Low, Below Average, Above Average or High for your age and sex. It sends a low cardio fitness notification when you fall in the lowest fifth for your age decade (ages 20 to 59), or below 18 mL/kg/min for men and 15 for women from age 60, per Apple's white paper. Classifications start at age 20, and the supported range is 14 to 65 mL/kg/min.
- Garmin shows Poor, Fair, Good, Excellent or Superior, based on Cooper Institute data.
So "Above Average" on an Apple Watch and "Good" on a Garmin can describe the same number. Use the percentile chart above to compare across brands.
How accurate are watch estimates?
Watches don't measure oxygen. They estimate VO2 max from your heart rate against your pace or power during an outdoor workout, plus your age, sex, height and weight.
|
Source |
Device |
Result vs. reference |
|---|---|---|
|
Apple's white paper |
Apple Watch |
Average error 1.2 ± 4.4 mL/kg/min vs. a submaximal test (not a maximal lab test) |
|
Lambe et al., PLOS One, 2025 (30 adults) |
Apple Watch |
Underestimated by 6.07 mL/kg/min on average; mean absolute error 13.3% |
|
Mayo Clinic Proceedings: Digital Health, Apr 2026 (40 adults) |
Apple Watch Series 10 |
Underestimated by 6.25 mL/kg/min; error 13.2%; correct FRIEND percentile band for 14% of people |
|
JMIR Biomedical Engineering, 2024 (19 adults) |
Apple Watch Series 7 |
Error 15.8%; underestimated more in very fit people, overestimated in less fit people |
|
Firstbeat white paper (the algorithm behind Garmin) |
Garmin/Firstbeat |
Maker claims 95% accuracy (about 5% error) for running across 2,690 workouts |
The pattern across independent studies: Apple Watch reads low for most people, and its individual error is wide enough to move you a band or two on the chart. Garmin's 5% figure is the maker's own number. Firstbeat's paper also notes that if the watch's assumed maximum heart rate is off by 15 beats per minute, the error grows to about 7% to 9%.
Repeat readings are more consistent than single ones. Apple reports test-retest reliability (ICC) of 0.86 to 0.89 for its estimates, which is why the trend line is the useful part.
When to ignore a one-day spike or drop
A single reading can swing for reasons that have nothing to do with fitness:
- Wrong max heart rate. Garmin asks you to set your maximum heart rate for the most accurate estimate. If you leave the age-based default and it's wrong, the estimate drifts with it.
- Heart-rate medications. Apple says conditions or medications that limit your heart rate can cause an overestimate. Apple Watch lets you log beta blockers and calcium channel blockers in the Health app to adjust for this.
- The wrong kind of workout. Apple only uses Outdoor Walk, Outdoor Run and Hiking. Garmin needs at least 10 minutes outdoors above 70% of your maximum heart rate. Hills, trails, heat and stop-start city runs can all skew the pace-to-heart-rate math.
- A new watch or a data update. Apple needs at least 24 hours of wear plus several qualifying workouts before the first estimate, and the Health app may offer to update past estimates when its model improves. Garmin says early estimates "may seem inaccurate" until it learns from a few runs.
A shift that holds for several weeks of normal training means more than any one day.
What moves the number
Apple's guidance is that most people can raise VO2 max by increasing the intensity and frequency of cardio exercise. Apple calls cardio fitness a strong indicator of overall physical health; Garmin calls VO2 max an indication of athletic performance that should rise as fitness improves. A lab cardiopulmonary exercise test (CPET) measures it directly. If your watch flags low cardio fitness and you have health questions, that's a conversation for your doctor, not a chart.
Related terms
Sources
All checked Oct 6, 2026.
- Kaminsky LA et al., "Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing: Data from FRIEND," Mayo Clinic Proceedings, 2022: https://www.mayoclinicproceedings.org/article/S0025-6196(21)00645-5/fulltext (PubMed: https://pubmed.ncbi.nlm.nih.gov/34809986/)
- Apple Support, "Track your cardio fitness levels" (published Sept 14, 2026): https://support.apple.com/en-us/108790
- Apple, "Using Apple Watch to Estimate Cardio Fitness with VO2 max" (white paper): https://www.apple.com/healthcare/docs/site/Using_Apple_Watch_to_Estimate_Cardio_Fitness_with_VO2_max.pdf
- Garmin, Forerunner 70 Owner's Manual, "About VO2 Max. Estimates": https://www8.garmin.com/manuals-apac/webhelp/forerunner70/EN-SG/GUID-CE1612DB-3D39-41D8-9AAF-E3E8874D292A-4224.html
- Firstbeat, "Automated Fitness Level (VO2max) Estimation with Heart Rate and Speed Data" (white paper): https://firstbeat.com/wp-content/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf
- Lambe R et al., "Investigating the accuracy of Apple Watch VO2 max measurements: A validation study," PLOS One, 2025: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0323741
- "Accuracy of VO2 max Estimates From Apple Watch Series 10," Mayo Clinic Proceedings: Digital Health, 2026: https://pmc.ncbi.nlm.nih.gov/articles/PMC13141568/
- "Assessing the Accuracy of Smartwatch-Based Estimation of Maximum Oxygen Uptake Using the Apple Watch Series 7," JMIR Biomedical Engineering, 2024: https://biomedeng.jmir.org/2024/1/e59459