How it works
This calculator uses the running equation from the American College of Sports Medicine (ACSM). It predicts how much oxygen you use each minute from your running speed and the incline. Burning food with one liter of oxygen releases about 5 kilocalories, so oxygen use converts straight into calories.
Two numbers come out:
- Calories burned is the total, including what your body would have used at rest over the same time.
- Above resting leaves out that resting part, so it shows the extra energy the run itself cost.
Body weight matters because you carry it every stride: the estimate rises in proportion to weight.
The formula
S = speed in meters per minute
G = incline as a fraction (2% = 0.02)
VO2 = 0.2 × S + 0.9 × S × G + 3.5 (ml per kg per minute)
calories = VO2 × weight (kg) × minutes × 5 ÷ 1000
above resting = (VO2 − 3.5) × weight (kg) × minutes × 5 ÷ 1000Worked example
A 70 kg runner covers 10 km in 1:00:00 on flat ground.
- Speed: 10,000 m ÷ 60 min = 166.7 m per minute.
- Oxygen use: 0.2 × 166.7 + 3.5 = 36.8 ml per kg per minute.
- Calories: 36.8 × 70 × 60 × 5 ÷ 1000 = 774 kcal.
- Above resting: (36.8 − 3.5) × 70 × 60 × 5 ÷ 1000 = 700 kcal.
The one-calorie rule of thumb
The ACSM equation contains a handy shortcut. On level ground, running costs 0.2 ml of oxygen per kilogram for every meter, which is 200 ml per kilogram per kilometer. At 5 kcal per liter, that works out to about 1 kcal per kilogram of body weight per kilometer above resting.
So a 70 kg runner uses roughly 70 kcal per kilometer on top of their resting energy, whether they run the kilometer in 5 minutes or 7. In miles, that is about 1.6 kcal per kilogram, or about 0.73 kcal per pound.
Questions
Does running faster burn more calories per kilometer?
Only a little. In the ACSM equation the cost of each level kilometer above resting is the same at any running speed. Running faster burns more calories per hour, and slightly fewer per kilometer in total because you finish sooner and spend less resting time on the clock.
Why does my watch show a different number?
Watches usually estimate calories from heart rate, age, weight and their own models, and some count total calories while others count only active ones. Large differences between devices and formulas are common, so compare numbers from the same source over time.
Should I use total or above-resting calories?
For topping up food around training, the above-resting figure is closer to the extra energy the run cost. The total figure is the number most apps and watches show.
How accurate is this estimate?
It describes an average runner. Running economy differs between people, and heat, wind, terrain and fatigue all change the real cost. Use it as a good estimate, not an exact measurement.
Can I use it for walking?
No. The running equation overestimates at walking speeds, roughly below 8 km/h (5 mph). ACSM uses a separate equation for walking.
Add this calculator to your site
Running club, coach or blog? You can put this calculator on your own site for free. Copy the code below into your page’s HTML. The calculator updates itself whenever we improve it.
The short script lets the frame grow to fit the calculator on your page. Please keep the credit line underneath it.
Sources
- American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 11th ed. Wolters Kluwer; 2021. Metabolic equations for running.