Running Economy Calculator

VO2 in this calculator is expressed in milliliters of oxygen per kilogram of body weight per minute -- a rate that's already normalized per kilogram -- so it depends only on Running Speed under both the Daniels and ACSM formulas. Body Weight is used afterward, purely to convert that per-kilogram rate into an absolute calorie burn per minute and per mile, which is why a heavier runner burns more total calories at the same speed even though their VO2 reading in ml/kg/min stays identical.

Both are published equations for estimating running VO2 from speed, but they were derived from different datasets and have slightly different shapes -- Daniels' formula (used in his VDOT training system) includes a small quadratic term that curves upward at higher speeds, while the ACSM equation is purely linear. They typically produce close but not identical estimates at a given speed, which is why both are shown side by side rather than presented as a single definitive number.

Calories per Mile is derived in two steps: the Daniels VO2 estimate (in ml/kg/min) is converted to an absolute oxygen consumption rate using Body Weight and the standard approximation that one liter of oxygen consumed corresponds to about 5 kilocalories burned, then that calorie-per-minute rate is multiplied by how many minutes it takes to cover a mile at the entered speed. Because pace slows and VO2 rises together at faster speeds, calories per mile tends to change less across speeds than either factor alone.

No -- it's an illustrative relative scale built into this calculator, not a peer-reviewed or universally standardized classification. Published running-economy research reports a range of "good" or "elite" values that vary by study population, testing protocol, and whether measurements were taken on a treadmill or overground, so treat the rating as a rough self-comparison rather than a definitive fitness label.