Calories burned by activity

How it works

Each activity has a MET value (intensity). Calories burned are estimated as MET × weight in kg × hours. It's an average estimate: real burn depends on intensity, age and body.

Note

For very intense or very light activities the value can vary: use it as a rough reference.

What a MET really is

One MET is the consumption of a person sitting still: about 3.5 millilitres of oxygen per kilo per minute, which corresponds roughly to one kilocalorie per kilo of body weight per hour. An activity rated at 8 MET therefore uses eight times that value, which is why the formula is simply MET times kilos times hours.

The system was born in the 1960s as a reference table and is periodically updated by a compendium published by researchers. It has an enormous virtue, namely that it lets you compare wildly different activities with a single number, and an equally large flaw: it is an average over average people.

Why the estimate errs, and by how much

Because the MET is calibrated on a standard person, and real consumption depends on things the table does not know. Training: someone who has run for years uses less to do the same thing, because they are more efficient. Body composition: muscle burns, fat almost does not, and two people of the same weight can differ considerably.

Then age, then sex, temperature and technique. On a single session the gap between estimate and reality can easily reach twenty or thirty per cent, which is why the numbers from two different watches on the same workout hardly ever agree.

The number that inflates every calculation

Nearly every estimate, including those on gym machines, gives the total calories, not the extra ones compared with sitting still. But that person would have consumed something in the same time anyway: about one MET per hour. Over an hour of walking at 3.5 MET, the additional spend is therefore two and a half MET, not three and a half, that is nearly thirty per cent less.

It is a difference that matters when exercise goes into a calorie budget, and it is the main reason why «I burned four hundred calories» often leads to eating five hundred more and not understanding why the weight is not falling.

What it is good for anyway

For comparing: between running and swimming, between an hour of easy cycling and half an hour of hard riding, between the stairs and the lift over a year. On that the MET is reliable, because even if the absolute value is imprecise the error is similar in both activities and the ratio holds.

And for scaling back expectations: an hour of moderate activity almost always falls between two and four hundred calories, that is far less than people believe and far less than it is easy to eat in five minutes. It is why, for weight, what you eat counts more than what you burn, while for health exactly the opposite is true.

Nearby tools

For daily needs there is Calorie needs and Basal metabolic rate, for a weight goal Calorie deficit. For specific activities Walking calories and Pace calculator.