Every calorie-burned-by-activity number you have ever seen — on a fitness app, a gym poster, a nutrition label’s activity chart — ultimately traces back to a MET value, whether or not it says so. Understanding what a MET actually is changes how much weight you should put on any of those numbers, including the ones this site’s own calculator gives you.
What a MET is
MET stands for metabolic equivalent of task. The 2024 Adult Compendium of Physical Activities — the authoritative published source most calorie-burn tools ultimately draw from, including the one on this site — defines one MET as 1 kilocalorie per kilogram of body weight per hour, which is roughly what your body burns lying completely still. An activity rated at 5 METs costs five times that resting rate. The arithmetic falls straight out of the definition: calories = MET u00d7 body weight in kg u00d7 hours, which is exactly what the calories burned calculator computes for any of 33 published activities.
The number almost nobody reports: net versus gross
This is the part every calorie-burn estimate you have seen has probably left out. Because a MET is a multiple of your resting rate, the number it produces already includes the calories you would have burned lying still for that same hour. An hour of gentle yoga at 2.3 METs comes out to 161 kilocalories gross for a 70-kilogram person — but 70 of those kilocalories would have been spent resting regardless. The yoga itself only added 91. Reporting 161 as “calories burned by yoga” overstates what the activity actually did by more than three quarters. At higher intensities this gap shrinks to a rounding error — an hour of running at 12 METs is 840 gross and 770 net, the same 70-kilocalorie resting baseline now barely moving the number — which is exactly why the gap matters most for the gentle end of the activity list and least at the vigorous end.
Why your watch disagrees with this number
Most wearables estimate calories from heart rate, not from a published MET table, and heart rate responds to things that have nothing to do with energy expenditure — caffeine, heat, stress, simple anxiety about a deadline. Neither method is measuring your actual metabolism directly; both are estimates built on different proxies, and they will not agree with each other or with a lab measurement. Treat any calorie-burn figure, from any source, as an estimate with real spread around it rather than a count.
What actually moves the number
- Body weight scales the result linearly — a 100-kilogram person burns 43% more than a 70-kilogram person doing the identical activity, because the unit is calories per kilogram per hour.
- Intensity, not just activity type, matters — “walking” spans a 3.0 MET stroll and a 5.5 MET brisk pace, nearly double the rate for what a casual glance might call the same activity.
- Time is the multiplier everyone already understands, and it is the one variable that behaves exactly as intuition suggests.
Why “burn 500 calories a day” targets are harder to hit through exercise alone than they sound
Five hundred kilocalories sounds like a modest daily target until it is measured against how long common activities actually take to reach it. At a brisk 4 mph pace (5.5 METs), a 70-kilogram person burns roughly 6.4 kilocalories a minute gross — meaning 500 gross kilocalories takes around 78 minutes of continuous brisk walking, and the net figure above resting is smaller still. This is not a reason to dismiss exercise as a tool — activity carries benefits the calorie count alone does not capture — but it does explain why “just walk it off” underestimates the time commitment required, and why combining activity with attention to intake, as the macronutrient split calculator and daily calorie needs calculator help with, tends to be more realistic than relying on exercise volume alone.
Why intensity matters more than the activity’s name
“Walking” is not one intensity — the published MET table spans roughly 2.0 for a slow amble to over 6 for a fast uphill pace, more than triple the energy cost for activities that would all get described with the same single word in casual conversation. This is exactly why a useful calorie estimate needs a specific pace or perceived effort, not just an activity category, and it is why fitness trackers that only ask “what activity are you doing” rather than measuring actual pace or heart rate tend to produce estimates with wide error bars — the underlying MET value they are assuming may not match what you actually did at all.
How to use this
If you are trying to understand what an activity actually cost you above resting, use the net figure, not the gross one — especially for lower-intensity activities, where the two numbers diverge the most. And treat the result as a genuine estimate: the published MET values are averages measured across groups of adults, not a measurement of your specific body on your specific day.
