VO₂ Max on Your Watch: What the Estimate Can Tell You

A watch can estimate aerobic fitness without a laboratory test. The trend can be useful, but the displayed VO₂ max is still an estimate with meaningful individual error.

The short answer

Yes—as a rough estimate and trend, especially when the device uses exercise data. No—as a replacement for a laboratory measurement when individual precision matters.

What VO₂ max actually represents

VO₂ max describes the maximal rate at which your body can use oxygen during intense exercise. In a lab it is measured from respiratory gases during a graded test. A watch usually estimates it from heart rate, pace or power, demographics and a proprietary algorithm.

How accurate are wearables?

A 2025 systematic review found acceptable or valid VO₂ max estimates in several studies, particularly using exercise data. Earlier INTERLIVE work found exercise-based algorithms had little average bias but wide limits of agreement—meaning the population average can look good while an individual's number is still off.

Why the trend may be more useful than the exact number

If you use the same device, train in similar conditions and the estimate rises over months alongside better performance, that is useful feedback. Comparing a Garmin estimate with an Apple estimate—or treating a one-point drop as lost fitness—is much shakier.

What can distort the estimate

Poor heart-rate readings, heat, hills, fatigue, medication, unusual terrain and too little qualifying exercise can all affect the algorithm. Different brands also use different models.

When a lab test is worth it

Athletes making precise training decisions, clinical exercise testing and research may need direct measurement. Most recreational exercisers can use the watch as a directional fitness signal rather than a medical-grade value.