The physics behind the number
Running costs roughly 1 kcal per kilogram per kilometre, with a modest speed penalty. The calculator uses the ACSM metabolic equation, which converts your speed into oxygen consumption and then into energy: about 5 kcal per litre of oxygen. For a 70 kg runner covering 10 km in 55 minutes, that comes out near 700 kcal.
Why pace matters a little
Faster running burns more per minute but less per kilometre, because you cover the distance sooner. The net effect is small: the same 10 km at 6:00 and 5:00 per kilometre differs by roughly 5%. Distance, not speed, is the dominant term — which is why the per-kilometre figure is the useful one for planning.
What the estimate leaves out
Terrain, heat, wind and running economy all move the real number by 5–15%. So does body composition: the equation uses total mass, so a muscular runner burns more than a lighter one at the same pace. Treat the result as a planning figure, not a laboratory measurement, and do not eat back every calorie it reports.
Frequently Asked Questions
How many calories does running burn per km?
About 1 kcal per kg of body weight per kilometre. A 70 kg runner burns roughly 70 kcal per km regardless of pace.
Does running burn more than walking?
Per kilometre, only slightly — walking is about 0.75 kcal/kg/km. Per minute, running is much higher because you cover more ground.
Should I eat back the calories?
Usually not. Estimates are imprecise and appetite responds to training in ways the arithmetic does not capture.
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Privacy & your data
SwimRunPace calculates everything in your browser. Distances, times and body weights are never uploaded — there is no account, no server-side record and no training history stored between visits.