What a 'MET' Is and How Exercise Calorie Estimates Really Work

Where "300 calories burned" comes from

Every treadmill, app, and watch confidently announces how many calories you just burned. It feels like a precise measurement, but behind that number is a single value assigned to your activity — the MET — plus your weight and your time. Understanding what a MET is does two useful things: it lets you compare activities sensibly, and it stops you treating a calorie readout as gospel when it's really an educated estimate.

What a MET actually measures

MET stands for metabolic equivalent of task. It's a measure of how hard an activity works your body relative to doing nothing:

• 1 MET is your resting metabolic rate — the energy you burn sitting quietly. It's about 1 calorie per kilogram of body weight per hour.
• An activity rated at 4 METs uses four times that resting energy.
• 8 METs means eight times resting — vigorous effort like running.

So a MET is really an intensity rating. Walking briskly is around 4.3 METs; jogging about 8; running hard, 11 or 12; gentle yoga, 2.5. Researchers have catalogued MET values for hundreds of activities in a reference called the Compendium of Physical Activities, which is where calculators get their numbers. The Calories Burned Calculator uses these values so you can compare activities on a level footing.

The calorie formula

Turning a MET value into calories is straightforward:

Calories = MET × body weight (kg) × time (hours)

Or, per minute: MET × 3.5 × weight in kg ÷ 200.

Three inputs, three levers: the activity's intensity (MET), your body weight, and the duration. A 70 kg person running at 10 METs for half an hour burns roughly 10 × 70 × 0.5 = 350 calories. Double the time or pick a higher-MET activity and the number rises in proportion.

Why body weight is in the equation

People sometimes wonder why a calorie estimate asks their weight. The answer is physics: moving more mass takes more energy. A heavier person running the same route at the same pace burns more calories than a lighter one, simply because there's more of them to move. That's why two people can do an identical workout and legitimately burn different amounts — and why a formula that ignored weight would be useless. It also means weight loss itself gradually lowers the calories a given workout burns, as there's less mass to carry.

The honest truth: these are estimates

Here's the part the glowing treadmill display won't tell you. MET values are population averages. They assume an "average" person performs the activity with "average" efficiency — and nobody is exactly average. Your fitness, running economy, muscle mass, and even the terrain all shift the real number.

Fitness trackers try to improve on raw METs by adding heart rate and motion data, but they're still estimating, and different devices use different algorithms that openly disagree with each other. Independent studies have repeatedly found consumer trackers off by 20% or more on energy expenditure. None of this makes the numbers useless — but it does mean you should read "347 calories" as "roughly 300-and-something," not a precise ledger entry.

How to use the numbers well

Given the uncertainty, the smart approach is relative, not absolute:

• Compare activities. METs reliably tell you that running burns more than walking, and swimming more than yoga. That ranking is trustworthy even when the exact calories aren't.
• Track trends, not totals. If your estimated weekly burn is climbing, you're doing more — useful regardless of the absolute figure.
• Don't "eat back" every estimated calorie. Because estimates run high, treating a workout as licence to eat an exact matching amount is a classic way to stall progress.

For body composition, the week's overall energy balance and consistency dwarf the precise burn of any single session.

Estimating your burn

Pick an activity, enter your weight and duration, and the Calories Burned Calculator gives a MET-based estimate with the rate per minute and hour. To understand the baseline calories your body uses at rest, see the BMR Calculator.

Sources

1. Ainsworth, B. E. et al. Compendium of Physical Activities — the standard MET reference.
2. American College of Sports Medicine (ACSM). Metabolic equations and energy expenditure.
3. Independent validation studies on consumer wearable energy-expenditure accuracy.

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This article is for general informational and educational purposes only and is not medical or dietary advice. Calorie figures are estimates based on averages. Consult a healthcare professional for personalised guidance.