How calories are calculated

Using the MET method (Metabolic Equivalent of Task):

Calories (kcal) = MET × body weight (kg) × duration (hours)

MET values come from the Compendium of Physical Activities (Ainsworth et al., 2011). 1 MET = 1 kcal/kg/h = resting metabolic rate.

What MET values mean

MET range	Intensity	Examples
1-3	Light	Walking slowly, yoga, desk work
3-6	Moderate	Brisk walking, leisure cycling, easy swimming
6-9	Vigorous	Running at 8-11 km/h, soccer, tennis
9-12	Very vigorous	Running at 12-16 km/h, fast cycling, HIIT
12+	Maximal	Sprinting, competitive racing

A 70 kg person running at 10 km/h (MET ≈ 9.8) for 45 minutes:

9.8 × 70 × 0.75 = 515 kcal

These are estimates. Actual burn varies with fitness level, body composition, and technique.
The formula counts gross calories (including basal metabolic rate). Net calories above rest are slightly lower.
For running, terrain, heat, and carried weight significantly affect actual burn.
Individual variation can be ±15-20% from the MET-based estimate.