Garmin vs Apple Watch: VO2max compared
How Garmin and Apple Watch estimate your VO2max, what each needs from you, what else they show and what independent studies say about accuracy.
| Garmin | Apple Watch | |
|---|---|---|
| Called | VO2 Max. | Cardio Fitness |
| Algorithm | Garmin in-house, built on Firstbeat Analytics | Apple in-house |
| App | Garmin Connect | Health app (iPhone) |
| From: Outdoor run | Yes | Yes |
| From: Walk | Yes | Yes |
| From: Treadmill | No | No |
| From: Bike (power meter) | Yes | Not confirmed |
| From: Resting test | Not confirmed | Not confirmed |
| From: All-day data | Not confirmed | Yes |
| Fitness age | Yes | Not confirmed |
| Race predictor | Yes | Not confirmed |
| Published accuracy studies | 5 | 3 |
| What you need to do | Run outdoors with GPS for at least 10 minutes at 70%+ of max heart rate, or ride steadily at high intensity for 20+ minutes with a power meter. Set up your user profile and max heart rate. | Wear the watch for at least 24 hours, then do several Outdoor Walk, Outdoor Run or Hiking workouts in the Workout app. Fairly flat ground, good GPS and heart rate signal help. |
Key differences
- Fitness age: Garmin shows one (not confirmed for the other).
- Race predictions: Garmin has them.
- Accuracy evidence: we found 5 published studies for Garmin and 3 for Apple Watch.
How each one works
Garmin: Compares your heart rate (wrist or chest strap) with your GPS pace on outdoor runs, or with power from a power meter on rides. It learns over several activities, so early numbers may be off.
Apple Watch: Measures how hard your heart works (heart and motion sensors, GPS) during outdoor walks, runs and hikes, plus passive outdoor walking. It also uses your age, sex, weight, height and heart-rate medications.
Which is better for VO2max?
For VO2max specifically, the best device is the one that sees your hardest efforts: if most of your training is outdoor running, both give an estimate (both use outdoor run, walk). If you cycle with a power meter, walk more than you run, or want a resting test, check those rows above. Whichever you choose, compare the number with itself over time and with the norms for your age.
Accuracy studies
Garmin
- Howard et al., J Med Eng Technol, 2026: Forerunner 265 overestimated VO2max (43.95 vs 41.10 ml/kg/min at start) but mean absolute percent error stayed under 10%.
- Engel et al., Eur J Appl Physiol, 2026: Forerunner 245 underestimated VO2max by about 4-5 ml/kg/min (MAPE 7.2-7.9%); error was larger in highly trained athletes (MAPE 9.4-10.4%).
- Carrier et al., Sensors, 2025: fēnix 6 VO2max estimates were judged accurate (MAPE 7.05%, concordance 0.73 vs 30 s lab average).
- Düking et al., J Sports Sci Med, 2024: Forerunner 245 in youth soccer players: MAPE 5.58% after one run and 1.06% after a second run.
- Passler et al., Int J Environ Res Public Health, 2019: Forerunner 920XT had a MAPE of 7.3% but significantly underestimated VO2max.
Apple Watch
- Lambe et al., Mayo Clin Proc Digit Health, 2026: Series 10 underestimated VO2max by 6.25 ml/kg/min on average; MAPE 13.2%; poor individual agreement.
- Lambe et al., PLoS One, 2025: Apple Watch underestimated VO2max by 6.07 ml/kg/min on average; MAPE 13.31%.
- Caserman et al., JMIR Biomed Eng, 2024: Series 7 estimate was lower than the lab value (41.37 vs 45.88 ml/kg/min); MAPE 15.79%, ICC 0.47.
Frequently asked questions
Is Garmin or Apple Watch more accurate for VO2max?
Garmin has more published validation (5 vs 3 studies). Watch estimates are typically within several ml/kg/min of lab tests for groups, with larger individual errors, so use either one to track your trend.
Does Garmin measure VO2max from outdoor run like Apple Watch?
Yes: both estimate from outdoor run, walk.
Which is better for VO2max: Garmin or Apple Watch?
Pick the one whose data sources match how you train: Garmin uses outdoor run, walk, bike (power meter); Apple Watch uses outdoor run, walk, all-day data.
Built from official documentation (see each brand page for sources). Features vary by model and firmware. Garmin and Apple Watch are trademarks of their owners; VO2max Health is independent and not affiliated with either.