How it works
VO₂ = 0.2·S + 0.9·S·grade + 3.5; kcal = VO₂ · weight ÷ 1000 · 5 · minutes
The ACSM equation estimates oxygen uptake from speed in meters per minute: 0.2 ml per kilogram per minute for each unit of horizontal speed, another 0.9 × speed × grade whenever the road tilts up, and a constant 3.5 — one MET, the cost of sitting still. Oxygen then converts to energy at about 5 kcal per liter, so the tool multiplies VO₂ by your mass, scales to liters, applies the 5, and spreads that per-minute burn across your duration. Two things follow: calories track body weight almost one-for-one, and the total is gross — with the default 70 kg and 50:00 entries, roughly 60 of the kcal shown would have been burned doing nothing at all.
Sources
- ACSM metabolic equations American College of Sports Medicine, “ACSM’s Guidelines for Exercise Testing and Prescription.” The running equation: VO₂ = 0.2·S + 0.9·S·grade + 3.5 (S in m/min).
- Oxygen-to-energy conversion Approximately 5 kcal are released per litre of oxygen consumed — the caloric equivalent used to convert VO₂ to energy expenditure.
- MET concept One MET = 3.5 ml O₂·kg⁻¹·min⁻¹ (resting metabolic rate); intensity is often expressed as a multiple of this baseline.
FAQ
When should I use the running calories burned calculator?
After a run you want to log honestly, or before a long one you need to fuel. A 70 kg runner covering 10 km lands in the 700–800 kcal range — context that helps decide whether a session calls for mid-run carbs or just a proper meal afterwards.
What inputs matter most?
Weight, by a wide margin: the equation multiplies everything by your mass, so a 100 kg runner burns about twice what a 50 kg runner does over the same course. Distance and time together set the speed term, and incline only matters when the route actually climbed.
Are these gross or net calories?
Gross, which makes them comparable to what a fitness watch reports — the resting 3.5 term keeps ticking during the run. If you are weighing training burn against a diet target, the true exercise-only figure is slightly lower than the number shown.
Does this work in miles and pounds as well as metric?
Yes — distance toggles between km and mi, weight between kg and lb, and every value is converted internally before the equation runs, so the estimate comes out identical whichever units you enter.
Why might my real-world burn differ?
The ACSM model describes an average runner on steady footing. Individual running economy varies, wind and soft trails raise the true cost, and downhill grades are not credited back. Treat the output as reliable for comparing your own runs, not as calorie-exact.
Can beginners use it?
Yes — it needs only body weight plus the distance and time of any run. Leave incline at 0 unless the route noticeably climbed, and note that slower sessions still add up, because duration multiplies the per-minute burn.
Calorie totals here are population-level estimates from the ACSM running equation, not measurements of your metabolism, and individual economy can move the real figure meaningfully. Do not build aggressive calorie deficits on them — food and weight decisions belong with a qualified professional.