By Zencalcy Editorial TeamLast reviewed About us
Divide your power by your body mass to get watts per kilogram, the measure that lets riders of different sizes be compared fairly. The result comes with a plain descriptive band that puts the number in broad context. It is most useful when you pair it with how long you can hold that power.
Turn watts and body mass into watts per kilogram.
watts per kilogram = power (W) ÷ body mass (kg)
The bands are broad labels for context only. They are not measured standards, and they say nothing about how long you can hold the power. A five-second sprint and a one-hour effort sit at very different numbers.
| Symbol | Meaning |
|---|---|
| power | The power you produced, in watts, at the effort you are judging. |
| body mass | Your body mass in kilograms. |
Producing 280 W at 70 kg gives 4.0 W/kg, a strong amateur or club racer level. The same 280 W at 60 kg is 4.67 W/kg, which shows why lighter riders climb on fewer absolute watts.
Power to weight divides your sustained power in watts by your body mass in kilograms, giving watts per kilogram. A rider producing 250 watts at 70 kilograms holds about 3.57 watts per kilogram, while the same 250 watts at 60 kilograms gives 4.17. The ratio matters because climbing power must lift your mass against gravity, so a lighter rider needs fewer watts to climb at the same speed.
On steep gradients the gravity term dominates the power equation, and it scales directly with total mass including the bike. That is why the watts per kilogram figure predicts climbing performance far better than raw watts, and why two riders with equal power can climb at very different speeds.
Sustained watts per kilogram over a long climb is a common way to compare climbers, while short bursts reflect anaerobic capacity. As a rough guide, a trained recreational rider may hold around three watts per kilogram for a long effort, a strong amateur nearer four, and professional climbers higher still for the duration of a hard climb.
The figure changes with the duration over which you measure it. A five second peak can be many times your one hour number, because power falls as the effort lengthens. Always compare watts per kilogram at the same duration and under similar conditions, or the comparison means very little.
Continue with the Bike Calorie Calculator, Bike Frame Size Calculator, or the Bike Gear Ratio Calculator — or browse more cycling tools and all sports calculators.
It adjusts power for size, so a light rider and a heavy rider can be compared on climbing and acceleration, where lifting body mass against gravity dominates.
Every result is computed locally in your browser from the formulas shown above. Nothing you type is uploaded, logged, or stored, and no account is required.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026