CalcVitalsCalories Burned Calculator — By Activity
Activity energy cost is worked out in METs — multiples of resting burn. Running at 5 mph is 8.3 METs, so a 70 kg person burns about 291 kcal in 30 minutes of it (8.3 × 70 kg × 0.5 h). Heavier bodies and longer sessions scale in direct proportion.
How it works
The MET system is how exercise science files the energy cost of everything humans do. One MET is your resting burn (about 1 kcal per kilogram per hour); every activity in the Compendium of Physical Activities is catalogued as a multiple of it, measured in laboratories across thousands of subjects. Calories then follow from one multiplication: METs × your weight × hours.
The formula's fairness is also its limitation — it knows your weight and the activity, but not your fitness, technique or terrain. An efficient runner burns a few percent less than the table at the same speed; a novice swimmer, far more. Hills, wind, heat and load all move the true figure. Treat the result as a solid central estimate with a genuine ±20% band, and be suspicious of any device or page claiming to know your burn to the nearest calorie.
For weight management there is one more subtlety, printed in the last row: the net burn above resting is what an activity adds to your day. If you are adding exercise calories back into a food budget, the net figure is the honest one to use — the gross figure quietly counts your resting burn twice.
The method
Calories = MET × weight (kg) × duration (hours). MET values from the 2011 Compendium of Physical Activities (Ainsworth et al.). Net burn subtracts 1 MET of resting expenditure for the same duration.
Frequently asked questions
Why does my watch give a different number?
Watches estimate from heart rate, motion and their own models, and independent testing puts them within roughly ±20–30% for energy (heart rate itself they measure well). The MET figure and the watch are both estimates; averaging their message is wiser than trusting either to the calorie.
Do heavier people really burn more doing the same exercise?
Yes — moving more mass costs more energy, roughly in proportion to weight for weight-bearing exercise like walking and running. It is one reason the same programme produces faster early loss in larger bodies.
Should I eat back the calories I burn?
If your calorie target was set from an activity level that already includes this exercise, eating them back double-counts. If the exercise is extra to the life your TDEE assumed, eating back the net figure (or half of it, to allow for estimation error) is reasonable.