Calories Burned Calculator

The idea behind the number

So you picked an activity, put in your weight and how long you did it, and the tool handed back a number of calories. The fair question is where that number actually comes from, and how much to trust it. Here is the honest version.

Everything here runs on one idea: the MET, short for Metabolic Equivalent of Task. A MET is just a multiple of the energy your body burns sitting still. Sitting quietly is 1 MET. An activity rated at 4 METs burns roughly four times the energy of sitting, 8 METs about eight times. Every activity in the dropdown carries a MET value, and the harder, heavier ones carry bigger numbers.

Here is a way to picture it. Think of a MET as the gear your body is in. First gear is lying on the sofa. Cooking dinner is second. A brisk walk is a few gears up, and an all-out run is near the top of the box. The MET value is simply which gear the activity puts you in, and the tool works out the fuel that gear burns for a body your size.

The formula it runs

Plenty of calorie pages hide the maths. There is no reason to, so here it is:

Calories = MET × 3.5 × weight (kg) × time (minutes) ÷ 200

Where do the 3.5 and the 200 come from? One MET is defined as burning 3.5 millilitres of oxygen per kilogram of body weight every minute, and your body releases about 5 calories of energy for every litre of oxygen it uses. Run that arithmetic and the awkward constants fold down into that one line. You do not have to touch any of it. Put your weight in as kilograms or pounds and your time in seconds, minutes or hours, and the tool converts everything before it does the sum.

The three numbers it gives you

This tool does not stop at one figure. It returns three, and each answers a slightly different question.

• Total calories burned. The headline: the energy for the exact activity and duration you entered.
• Calories burned per hour. The same effort stretched to a full hour, so you can line activities up against each other on even terms.
• Potential weight loss. This one needs a caveat, and we are not going to skip it. The tool divides your calories by 7,700, because roughly 7,700 calories is the figure often quoted for the energy stored in a kilogram of body fat. It is a rough rule, and it flatters reality. Real weight change is messier: your body adapts to burning more, some early loss is water rather than fat, and appetite tends to climb to meet the extra output. Read this as the theoretical ceiling for a single session, not a promise. One workout does not carve a neat slice off the scale.

A worked example

Take a 70 kilogram person cycling for 30 minutes, where the tool uses a MET of 9.5 for cycling. The sum runs like this:

Calories = 9.5 × 3.5 × 70 × 30 ÷ 200
Calories ≈ 349 kcal

Stretched to a full hour that is about 698 calories per hour. And dividing the 349 by 7,700 gives the roughly 0.05 kilogram weight-loss figure, which is exactly why no single ride shifts the scale by much.

Why it is an estimate, not a measurement

None of this is measured. It is built from population averages, and it is only fair to be clear about where it drifts.

• The baseline was one person. The 3.5 figure at the heart of the formula came from the resting oxygen use of a single 70 kilogram, 40 year old man, decades ago. When researchers later measured a large, mixed group of adults, the real average sat closer to 2.6, meaning the standard value overshoots actual resting burn by roughly a third for many people. In plain terms, this style of calculator tends to run a little generous, especially for people carrying more body fat, whose kilograms burn less at rest than the formula assumes.
• It counts every calorie, including the ones you would burn anyway. The number is your total energy for that time, not the extra on top of resting. Sit still for the same half hour and you would still burn something, so the true bonus from the activity is a little smaller than the headline.
• It cannot see how hard you actually went. Two people doing the "same" activity can differ a lot with fitness, technique, terrain and effort, and a single MET per activity cannot capture that.

So read the number as a solid ballpark, not a receipt. It is a useful way to compare activities and to track roughly how much you move. It is not accurate to the calorie, and no tool of this kind is. For more detail on the big cardio activities, the dedicated calculators break things down by intensity: walking, running, biking and swimming.

Questions people ask

Why does my fitness watch show a different number?

Your watch uses heart rate and your personal data to estimate effort moment by moment, while this tool uses a fixed average for the activity. Neither is exact. Treat both as estimates that bracket the truth rather than pin it down.

Does a heavier person burn more doing the same thing?

Yes, and the formula reflects it. Weight sits right in the equation, so a heavier body burns more covering the same time or distance, simply because there is more of it to move.

It refused to calculate for a low weight. Why?

Below about 40 kilograms this kind of average-based estimate becomes unreliable, so the tool stops and points you to a professional instead. That is deliberate, not a bug.

Is the calorie number gross or net?

Gross. It is the total energy for the time, including what your body would burn at rest anyway, so the real "extra" from the activity is a little lower.

Can I trust the weight-loss figure?

As a rough ceiling for one session, and no further. The note above explains why real weight change is messier than dividing by 7,700.

References

A word on the sources. The MET values behind each activity come from the Compendium of Physical Activities, the reference catalogue researchers use to put an energy cost on human movement. The definition of one MET, and the honest point that it overestimates resting burn for many people, come from Byrne and colleagues in the Journal of Applied Physiology.

1. Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise. 2011;43(8):1575-1581. https://doi.org/10.1249/MSS.0b013e31821ece12
2. Compendium of Physical Activities (browsable MET tables). https://pacompendium.com/
3. Byrne NM, Hills AP, Hunter GR, Weinsier RL, Schutz Y. Metabolic equivalent: one size does not fit all. Journal of Applied Physiology. 2005;99(3):1112-1119. https://doi.org/10.1152/japplphysiol.00023.2004