Rolling Resistance Power Calculator

Rolling resistance is the force that opposes a tire rolling on a surface, caused mainly by the tire deforming and recovering as it rotates. It is modelled as the rolling resistance coefficient times the normal load (vehicle weight). Unlike aerodynamic drag, rolling resistance force is roughly constant with speed, so the power it consumes rises in direct proportion to speed.

The force equals the rolling resistance coefficient (Crr) times the vehicle mass times the acceleration due to gravity: F = Crr times m times g, with g equal to 9.80665 metres per second squared. On level ground this is the steady force needed to keep the vehicle moving against tire losses, before adding aerodynamic drag.

Crr depends on the tire, inflation, load, and road surface, so it is not a universal constant. Car tires on smooth pavement commonly fall in a low range often cited around 0.01, with low-rolling-resistance tires lower and rougher surfaces higher. Because the value is conditions-specific, this calculator takes Crr as a user-editable input.

Power is force times velocity. Since rolling resistance force is approximately independent of speed, the power needed to overcome it grows linearly with speed: double the speed roughly doubles the rolling-resistance power. Aerodynamic drag, by contrast, rises with the cube of speed and dominates at higher speeds.

At low speeds rolling resistance is the larger road load; at higher speeds aerodynamic drag overtakes it because drag power scales with the cube of speed. The crossover depends on the vehicle. To estimate total road-load power, add the rolling resistance power from this calculator to the aerodynamic drag power and any grade load.