Cycling Speed From Power: What Your Watts Are Worth

Watts are the input and speed is the output, but the link between them is not a straight line. This estimator solves the resistance model for you.

What is the Cycling Speed From Power Calculator?

Enter your average power in watts, total rider-plus-bike weight, and the road gradient. The tool solves a simple resistance model (air drag, rolling resistance, and gravity) for speed. This is an estimate: real speed also depends on position, wind, tyres, and road surface.

How to use it

1. Enter your average power in watts.
2. Enter rider-plus-bike weight in kilograms.
3. Enter the gradient and click Estimate Speed.

Worked example

At 200 watts and 85 kg on the flat, the model solves to about 33.71 km/h (roughly 9.36 m/s), an estimate that ignores wind and riding position.

How fast is 200 watts on the flat?

Roughly 34 km/h for an 85 kg rider-plus-bike in this simple model (33.71 km/h in the tool), though position and wind can move the real number either way.

Frequently asked questions

Why is speed not proportional to power?

Air drag grows with the cube of speed, so each extra km/h costs more watts than the last.

Does it account for wind?

No. It assumes still air on a smooth road, so a headwind will lower real speed.

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