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Rolling Resistance Power Calculator

Enter mass, speed and the rolling resistance coefficient to find the power lost to rolling.

How it is calculated

The tool first finds the resisting force, then the power needed to push against it at your speed. F = Crr × m × g in newtons, where Crr is the dimensionless rolling resistance coefficient, m is the total mass in kg and g is gravitational acceleration in m/s². Speed is entered in km/h and converted with v = km/h ÷ 3.6 to m/s, and then P = F × v in watts. All four fields are required (a blank g gives no result). Crr and speed can be 0, mass and g must be above zero. The result covers rolling resistance only on level ground at constant speed; air drag, slopes, bearings and drivetrain losses are not included, and Crr is assumed constant with speed.

Worked example

A cyclist and bike weigh 85 kg in total, ride at 30 km/h on a surface with Crr = 0.005, using g = 9.81 m/s². Force = 0.005 × 85 × 9.81 = 4.17 N (4.169 before rounding). Speed = 30 ÷ 3.6 = 8.333 m/s. Power = 4.169 × 8.333 = 34.74 W. So about 35 watts of the rider's effort goes purely into rolling resistance at that speed. Doubling the speed to 60 km/h would double that to about 69.5 W, while the force stays at 4.17 N.

Try this example →

Common mistakes

  • Entering only the rider's weight. The mass is the total moving mass: rider, bike, clothing and any luggage or load.
  • Entering speed in m/s or mph. The field is km/h; 8.3 typed for 8.3 m/s is treated as 8.3 km/h and the power is about 3.6 times too low.
  • Using a Crr copied from a different tire, pressure or surface. Crr is the biggest unknown here and a rough road can change it a lot, so treat the result as an estimate for that exact condition.
  • Reading the power as the total effort. It is only the part for rolling resistance; at higher speeds air drag usually takes much more, and climbing needs extra power the tool does not include.
  • Typing the coefficient as a percentage. 0.5 would mean a Crr of 0.5, a hundred times larger than the 0.005 used in the example; enter it as a decimal.

Sources

About this calculator

Rolling resistance is the force that resists a wheel's motion as its contact patch continuously deforms and recovers against the road or ground, calculated as F = Crr × m × g, where Crr is the rolling resistance coefficient (a dimensionless value that depends on tire construction, pressure, and surface — asphalt, gravel, or a treadmill belt). Multiplying that force by speed gives the power being spent purely to overcome rolling resistance, separate from the power lost to aerodynamic drag or gained/lost to gradient.

This calculator takes mass, speed and a rolling resistance coefficient and returns both the resistance force and the power it costs to overcome. Cyclists and triathletes comparing tire choices, bike fitters and coaches building power-based training models, and mechanical engineers estimating vehicle drivetrain losses use it to isolate exactly how many watts a given tire or surface is costing at a target speed, which is one of the few variables a rider can meaningfully control alongside aerodynamics.

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Comments (1)

  • Editorial team

    The tool is most useful for comparing options rather than predicting a ride. Changing the coefficient from 0.005 to 0.004 for an 85 kg total load at 30 km/h saves about 7 W, which is the kind of gain a tyre swap is meant to deliver. Remember that air drag is left out, so the number is only one part of what the rider produces at speed. Which tyre or surface coefficients do you use?

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