Running Power Estimate Calculator
Running power is an estimate of the mechanical work rate a runner produces. It combines the power needed to lift the body against gravity on a slope with the metabolic cost of running on the flat. This calculator gives a transparent physical estimate from body weight, running speed, the gradient, and an energy-cost factor. It is a simplified model, not a force-plate measurement, and different running-power devices use different proprietary methods.
Running power estimate
Flat power (W) = cost * mass * speed
Slope angle (radians) = arctan(grade / 100)
Gravity power (W) = mass * 9.81 * speed * sin(slope angle)
Total power (W) = flat power + gravity power
Mass is in kilograms, speed in metres per second, and the energy cost in joules per kilogram per metre. The constant 9.81 is standard gravity in metres per second squared. The flat term uses the well-established approximate energy cost of running of about 3.8 J/kg/m, which is an editable input. The gravity term is the rate of doing work against gravity when climbing.
Worked example
For a 70 kg runner at 3.3 m/s on the flat (grade 0) with cost 3.8: flat power = 3.8 * 70 * 3.3 = 877.80 W, gravity power = 0 (no slope), total = 877.80 W. On a 5% grade, slope angle = arctan(0.05) = 0.04996 rad, gravity power = 70 * 9.81 * 3.3 * sin(0.04996) = 70 * 9.81 * 3.3 * 0.04994 = 113.16 W, so total = 990.96 W.
Frequently asked questions
Why does running power differ between devices?
Unlike cycling, running power has no single agreed measurement standard. Watches and pods estimate it from accelerometry and proprietary models, so values differ between brands. This tool uses an explicit physical model so you can see exactly what it includes.
What is the energy cost of running?
It is the metabolic energy used to move one kilogram of body mass one metre on the flat, often cited as roughly 3.6 to 4.0 J/kg/m and commonly approximated as 3.8. It is an editable input because it varies with running economy, surface, and speed.
Does this account for air resistance?
No. At typical running speeds air resistance is a small fraction of total cost, so this simplified model omits it. For windy conditions or very high speeds, the estimate will be slightly low.
Can I compare this to my watch's running power?
Treat it as an independent estimate rather than a calibration. Because devices use different models, absolute values may differ; the model here is most useful for understanding how speed and gradient drive power.
Sources
- Energy cost of running, di Prampero and colleagues, indexed at the U.S. National Library of Medicine: PubMed.
- U.S. National Institute of Standards and Technology: Standard acceleration of gravity (9.80665 m/s^2).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. Educational estimate for training. See our methodology.