Cycling Speed & Power Calculator

Which direction to solve the power equation:

• Speed from power: enter watts and get the resulting steady speed.
• Power from speed: enter a target speed and get the watts required to hold it.

The steady power you put into the pedals, in watts. The model finds the speed at which drag, rolling resistance and gravity exactly consume this power.

The steady speed you want to hold, in km/h. The model reports the watts needed to sustain it under the conditions below.

Your weight in kilograms, including clothing and shoes. Weight matters most on climbs through gravity, and a little through rolling resistance.

Weight of the bike plus everything on it — bottles, tools, bags — in kilograms. It is added to rider weight for the gravity and rolling terms.

Road gradient in percent: rise divided by distance, times 100. Positive values are uphill, negative downhill; leave 0 for flat roads.

Road surface sets the rolling-resistance coefficient (Crr): smooth asphalt rolls easiest, rough asphalt costs a little more, and gravel or MTB trail cost considerably more at the same speed.

Elevation above sea level in meters. Thinner air at altitude lowers air density and cuts aerodynamic drag — the same watts go noticeably faster at 2000 m than at sea level.

Percent of your power lost in the chain and drivetrain before it reaches the road. A clean, well-lubricated chain loses about 2 – 3%; a dirty or cross-chained drivetrain loses more.