CalcVitalsRunning Calories Calculator — By Distance & Weight
Running has a beautifully simple energy rule: about 1 kilocalorie per kilogram of body weight per kilometre, nearly regardless of speed. So a 70 kg runner burns about 714 kcal over 10 km, and roughly 3,000 kcal over a marathon.
How it works
Running is one of the few exercises whose energy cost can be stated as a proverb: a kilocalorie per kilogram per kilometre. It works because running is essentially a series of jumps that lift and move your mass — speed changes the power but not the total work per distance, which is why a slow 10K and a fast 10K cost nearly the same energy (the fast one just finishes sooner and feels harder).
The figure here uses 1.02 kcal/kg/km, the middle of the measured range for adults on level ground, and prints the range beside the result, because individuals genuinely differ: running economy varies with training, footwear, surface and form by about ±10%, and soft trails or hills add more. Any calculator or watch stating your run burn to the exact calorie is overstating its knowledge.
For fuelling, the practical translation: a marathon costs a 70 kg runner roughly 3,000 kcal, while the body's glycogen stores hold about 1,800–2,200 — the arithmetic origin of 'the wall', and the reason marathon fuelling plans exist. For weight management, remember these are gross figures unless you subtract the resting share for the time involved.
The method
Energy = distance (km) × weight (kg) × 1.02 kcal/kg/km (gross), with the published range 0.95–1.05 shown. Consistent with Compendium MET values across running speeds when duration is accounted. Net cost ≈ 0.95–1.0 of gross for typical durations.
Frequently asked questions
Does running faster burn more calories per km?
Barely — a few percent at most. Faster running burns much more per minute, but you finish sooner; per kilometre the cost is nearly flat. Walking, by contrast, is much cheaper per kilometre (about 0.6× running).
Why does my watch credit fewer calories?
Watches often display net calories and apply their own economy models. The difference between a watch's net figure and this page's gross figure is mostly the resting burn during your run — both can be 'right' about different quantities.
How many calories does a marathon burn?
About 42 × your weight in kg × 1.02: roughly 2,600 kcal at 60 kg, 3,000 at 70 kg, 3,450 at 80 kg. It is also why you cannot out-run a bad diet at shorter distances — a 5K costs a 70 kg runner only ~360 kcal.