Learn & Understand

The Currency of Exertion: What a MET Really Measures

Comparing a gentle yoga session to a punishing jump-rope workout seems impossible — until you have a common unit for effort. That unit is the MET, the metabolic equivalent, a clever standard that expresses any activity's energy demand relative to simply sitting still. It is the currency exercise science uses to measure exertion of every kind.

One Unit for Every Activity

The MET compares the energy an activity burns to the energy you would burn at complete rest. One MET is quiet sitting; an activity of four METs burns four times as much energy. This elegantly reduces the vast variety of human movement — walking, swimming, digging, dancing — to a single comparable scale of intensity, anchored to the body's resting baseline.

The Compendium of Activities

Exercise scientists painstakingly measured the energy cost of hundreds of activities and compiled them into a reference known as the compendium of physical activities. This tabulates a MET value for everything from sleeping to sprinting, giving researchers and calculators a standard figure for each. When a tool estimates the calories of a workout, it is drawing on this accumulated body of measurement.

Turning METs Into Calories

The MET becomes a calorie figure through a simple relationship involving body weight and time: a heavier person burns more energy at the same MET, and a longer session burns more than a short one. Multiply the activity's MET value by body weight and duration, and an abstract intensity becomes a concrete number of calories — the bridge from “I exercised” to an energy figure.

A Standard, Not a Certainty

MET values are population averages, not personal measurements. Two people doing the same activity can differ in real effort and efficiency, so a MET-based estimate is a reasonable approximation rather than an exact personal reading. Its value is comparison and consistency — a shared, standardized way to weigh one form of exercise against another.

Estimating Calorie Burn

To estimate calories from an activity's MET, use the Calorie Burn Calculator or the MET Calorie Calculator. For a heart-rate-based estimate instead, see the Exercise Calorie Estimator.