What a MET Actually Is
MET stands for metabolic equivalent of task. One MET is the oxygen cost of sitting quietly, approximately 3.5 ml O2 per kilogram of body weight per minute, which translates to about 1 kcal per kg per hour.
An activity rated 6 METs costs six times rest. The Compendium of Physical Activities catalogs hundreds of activities this way, which is why every calorie calculator quietly agrees with every other.
The Formula, Step by Step
Multiply the MET value by 3.5 to get ml O2 per kg per minute, multiply by body weight in kg, divide by 200 to convert oxygen to kilocalories, then multiply by minutes. A 75 kg runner at 9.8 METs burns about 12.9 kcal per minute.
Heavier bodies burn more per minute for the same activity, not because they're fitter, but because moving more mass costs more energy.
How Much to Trust the Number
The formula assumes steady-state effort and average economy; real burns vary ±20% with fitness, technique, terrain, and conditions. Heart-rate-based trackers narrow the error somewhat but are still estimates.
Use the number for planning and consistency, not accounting. What matters is the same activity compared across weeks.
Sources
FAQ
What does MET stand for?
Metabolic equivalent of task, a multiple of resting energy use; 1 MET equals sitting quietly.
How accurate is the MET formula?
Within roughly ±20% for steady-state activities; intervals, terrain, and individual economy shift the real value.
Why do heavier people burn more?
Moving a larger mass requires more energy, so the same activity burns more calories per minute at higher body weight.
Important disclaimer: Results are educational estimates, not a substitute for professional advice. Review your numbers with a qualified advisor before acting on them.