MET stands for Metabolic Equivalent of Task. It expresses the energy demand of a physical activity as a multiple of the resting metabolic rate. By definition, 1 MET equals the metabolic rate while sitting quietly — approximately 3.5 ml of oxygen per kilogram of body weight per minute, or roughly 1 kcal/kg/hour.
MET values for running range from about 7 (light jogging at 6–7 km/h) to 14+ (fast running above 14 km/h). The formula for calorie burn from MET values:
kcal = MET × weight_kg × duration_hours
For example, a 70 kg runner at MET 10 for 30 minutes: 10 × 70 × 0.5 = 350 kcal.
The standard reference for MET values in research is the ACSM Compendium of Physical Activities (Ainsworth et al., 2011), which catalogues hundreds of activities with their MET values derived from indirect calorimetry studies. This is the source used in the RunPaceLab calorie burn calculator.
Important limitations: MET values represent population averages. Individual running economy varies significantly. A highly efficient runner will burn fewer calories at the same MET pace than the formula suggests; a less efficient runner will burn more. The error range is approximately ±15–20%.