Apple Watch vs Oura Ring: VO2max compared
How Apple Watch and Oura Ring estimate your VO2max, what each needs from you, what else they show and what independent studies say about accuracy.
| Apple Watch | Oura Ring | |
|---|---|---|
| Called | Cardio Fitness | Cardio Capacity (VO2 Max) |
| Algorithm | Apple in-house | Oura in-house |
| App | Health app (iPhone) | Oura app |
| From: Outdoor run | Yes | Not confirmed |
| From: Walk | Yes | Yes |
| From: Treadmill | No | No |
| From: Bike (power meter) | Not confirmed | Not confirmed |
| From: Resting test | Not confirmed | Not confirmed |
| From: All-day data | Yes | Not confirmed |
| Fitness age | Not confirmed | Not confirmed |
| Race predictor | Not confirmed | Not confirmed |
| Published accuracy studies | 3 | 0 |
| What you need to do | 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. | Gen3 or later ring with an active membership. Brisk 6-minute walk on a straight, level route, location services on, phone carried, phone battery above 20%. Not possible on a treadmill. Oura suggests a test about once a month. |
Key differences
- Accuracy evidence: we found 3 published studies for Apple Watch and 0 for Oura Ring.
How each one works
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.
Oura Ring: A first estimate uses age, sex, height and weight (population averages). A guided 6-minute walking test then uses distance from phone GPS and ring heart rate to estimate VO2 max.
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 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
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.
Oura Ring
No published, peer-reviewed validation found.
Frequently asked questions
Is Apple Watch or Oura Ring more accurate for VO2max?
Apple Watch has more published validation (3 vs 0 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 Apple Watch measure VO2max from walk like Oura Ring?
Yes: both estimate from walk.
Which is better for VO2max: Apple Watch or Oura Ring?
Pick the one whose data sources match how you train: Apple Watch uses outdoor run, walk, all-day data; Oura Ring uses walk.
Built from official documentation (see each brand page for sources). Features vary by model and firmware. Apple Watch and Oura Ring are trademarks of their owners; VO2max Health is independent and not affiliated with either.