How it works
VO₂ = 0.2·S + 0.9·S·grade + 3.5; kcal = VO₂ · weight ÷ 1000 · 5 · minutes
The ACSM running equation estimates oxygen uptake VO₂ (in ml per kg per minute) from running speed S in metres per minute: a horizontal cost of 0.2·S, a vertical cost of 0.9·S·grade for any incline, and a resting 3.5 (one MET). Each litre of oxygen your body consumes releases about 5 kcal, so calories per minute = VO₂ × your weight in kg ÷ 1000 × 5, and total calories = that rate × the minutes you ran. Because the model is driven by speed and weight, a heavier runner or a faster pace burns more, and adding grade raises the vertical term. The figure is gross energy (it includes the calories you would have burned at rest); net exercise calories are slightly lower. We convert pounds to kilograms and miles to metres internally so the units never disagree.
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
How many calories does running burn?
It depends mostly on your body weight, how far and how fast you run, and the terrain. As a rough guide a 70 kg runner burns around 700–800 kcal over 10 km. This calculator gives a personalised figure from the ACSM equation rather than a one-size-fits-all number.
Does running speed change calories burned?
Yes. Faster running raises oxygen demand, so you burn more per minute. Over a fixed distance the difference is smaller — running the same distance faster burns somewhat more total energy and finishes sooner. The calculator captures this through the speed term in the ACSM equation.
Why does body weight matter so much?
Energy cost is roughly proportional to the mass you move, so calories scale almost directly with body weight. A 100 kg runner burns about twice as many calories as a 50 kg runner over the same run, which is why weight is the single biggest input.
Are these gross or net calories?
Gross — the total includes the small amount you would have burned at rest during that time (the 3.5 resting term). Net exercise calories are a little lower. Most fitness trackers and calculators report gross calories, so this is comparable to them.
Does incline increase calories burned?
Yes. Running uphill adds a vertical workload, which the equation models with the 0.9·S·grade term. Enter the average grade as a percentage and the estimate rises accordingly. Downhill running is more complex and is not added back here.
How accurate is the estimate?
It is a solid population-level estimate, but individual economy, fitness, surface and conditions all vary, so treat it as a guide rather than an exact measurement. For everyday tracking it is more than accurate enough to compare runs.
Calorie figures are estimates from the ACSM population equation and your inputs, not a precise measurement of your metabolism. Use them as a guide for training and fuelling, not medical or dietary advice.