Running calories:
what 8, 10 and 12 km/h really cost

What different running speeds cost

Run for 30 minutes at 8 km/h and a 70 kg person burns about 291 kcal. At 10 km/h the same half hour costs 350 kcal, and at 12 km/h about 403 kcal. Faster running clearly burns more each minute, and the reason is the intensity multiplier known as the MET.

A MET is the energy used at rest, set to 1. Running at 8 km/h works at about 8.3 times that, 10 km/h at roughly 10, and 12 km/h at about 11.5. These values follow the Compendium of Physical Activities for running on level ground; 8 and 12 km/h match listed speeds and 10 km/h sits between two of them.

Because the values are averages, the output is an estimate with some spread. Wind, hills, running economy and shoes all nudge the true cost, but the pattern is dependable.

The running calorie formula

To turn this into a per-kilometre figure, divide by the distance. Time at a steady speed equals distance divided by speed, so the weight and speed work out as: calories per km = MET × weight ÷ speed in km/h. That small rearrangement explains almost everything in the table below.

Worked example: 40 minutes at 10 km/h

An 85 kg runner does a 40-minute steady run at 10 km/h, covering 6.67 km.

Run the same 40 minutes at 8 km/h and the figure is 8.3 × 85 × 0.667 ≈ 470 kcal for 5.3 km, so the faster run adds about 96 kcal and 1.3 km.

Calories by speed and body weight

The table shows a 30-minute run for three body weights, using the MET values above.

Read across and the numbers climb steadily with speed. Read down and each extra 15 kg of body weight adds about 20% to the burn. A heavier body does more work against gravity on every stride, so the extra cost is real.

Calories per kilometre barely change

Divide each result by the distance covered and the speeds converge. For a 70 kg runner the cost per kilometre is about 73 kcal at 8 km/h, 70 kcal at 10 km/h and 67 kcal at 12 km/h. A 10 km run costs about 726, 700 and 671 kcal respectively.

The slight fall at higher speed is partly an artefact of the rounded MET table, since measured energy cost per kilometre in running is close to constant. The practical rule of thumb is about 1 kcal for every kilogram of body weight for every kilometre.

Scaling the rule to race distances

The one-calorie-per-kilogram-per-kilometre rule makes planning easy. A 70 kg runner uses about 350 kcal in a 5K, 700 kcal in a 10K, about 1,477 kcal across a half marathon (21.0975 km) and about 2,954 kcal across a marathon (42.195 km). These are gross figures, and the extra energy above resting is a little lower.

The net cost is worth knowing if you track a calorie deficit. Subtracting 1 MET gives 7.3 × 70 ÷ 8 ≈ 64 kcal per km at 8 km/h and 10.5 × 70 ÷ 12 ≈ 61 kcal per km at 12 km/h, which is close to 0.9 kcal per kilogram per kilometre. That is the number to use when asking how much a run adds to your day.

Long runs also draw on stored carbohydrate, which holds roughly 1,500 to 2,000 kcal in the muscles and liver for a typical adult. That is why events beyond about 90 minutes usually involve taking in fuel during the run. How much you need depends on pace, training and what you ate before, so test strategies in training rather than on race day.

One practical use of all this is choosing a speed for the goal. If you have 40 minutes and want to cover as much ground as possible, a faster pace gets you further for about the same energy per kilometre. If you want a longer, lower-stress outing, 8 km/h held for an hour gives about 8.3 × 70 = 581 kcal and 8 km, which most people recover from more easily than a hard 10 km/h effort. Both are valid; the better one is the pace you can repeat three times a week without injury or dread.

Why your running number may be off

• Treadmill versus road: with no wind resistance, set the treadmill to 1% incline to match outdoor effort.
• Hills: a climb can lift the cost well past the flat-ground MET, and the descent only returns part of it.
• Intervals: alternating fast and slow efforts produces an average MET, so entering average pace can understate the hard parts.
• Efficiency: experienced runners use slightly less energy at the same speed than beginners.
• Gross versus net: subtract 1 MET if you want only the extra energy, which lowers the 70 kg, 30-minute figure at 10 km/h from 350 to 315 kcal.

If you use one of the running calorie calculators on this site, enter a speed you actually held, not your goal pace. Ask a clinician before starting a running programme if you have heart, joint or other health concerns.