VO₂ max (maximal oxygen uptake) is the maximum rate at which your body can consume oxygen during intense exercise, expressed in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It is the gold standard measure of aerobic fitness and cardiovascular capacity. The higher your VO₂ max, the more oxygen your working muscles can use — and the faster you can run for longer.

VO₂ max is determined by the central cardiovascular system (how much blood the heart pumps per beat) and the peripheral muscles (how efficiently they extract and use oxygen). Training increases both components. Endurance training — particularly Zone 2 runs and VO₂max intervals — improves cardiac stroke volume and mitochondrial density, both of which raise VO₂ max over months of consistent training.

Laboratory measurement of VO₂ max requires running on a treadmill with a mask collecting exhaled gases. Field tests — the Cooper 12-minute run, Rockport walk test, beep test, and resting HR method — provide estimates within 5–10% of lab values. This calculator uses four validated field methods so you can choose the one that fits your fitness level and available equipment.