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Total Cycling Resistance Power Calculator

Total Cycling Resistance Power — calculate it instantly for your rides, free.

How it is calculated

The tool adds three forces that oppose the rider and multiplies by speed. Rolling: F_roll = Crr × m × 9.81 × cos θ. Gravity: F_grav = m × 9.81 × sin θ. Air: F_aero = ½ × ρ × CdA × v². Power is P = (F_roll + F_grav + F_aero) × v. Here m is total mass (rider plus bike) in kg, Crr is the dimensionless rolling coefficient, CdA is drag area in m², ρ is air density in kg/m³, speed is entered in km/h and divided by 3.6 to get v in m/s, and θ = atan(grade ÷ 100). The result is power at the wheel in watts. Drivetrain losses and wind are not included, and the result is one total, not a breakdown. A negative grade (descent) can give a negative result, meaning gravity alone exceeds the resistance. Speed must be above zero.

Worked example

An 80 kg rider and bike, Crr 0.005, CdA 0.32 m², air density 1.225 kg/m³, on a 2.5 % grade at 30 km/h. Speed: 30 ÷ 3.6 = 8.33 m/s. Rolling force is about 3.92 N, gravity about 19.61 N, and air drag 0.5 × 1.225 × 0.32 × 8.33² = about 13.61 N. Total force is about 37.15 N, and 37.15 × 8.33 gives 309.56 W. On the flat the same rider needs only 146.13 W, so the small climb roughly doubles the effort.

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Common mistakes

  • Entering speed in m/s or mph. The field expects km/h, so 8.3 for 8.3 m/s would be read as a very slow ride.
  • Using rider weight alone. Mass should include the bike, shoes, bottle and bag; leaving out 8 to 10 kg of kit understates the gravity and rolling terms.
  • Typing the grade as a fraction. A 5 % climb is entered as 5, not 0.05; 0.05 is read as a 0.05 % grade.
  • Expecting a drivetrain loss or a wind term. Neither is applied, so the number is power at the wheel in still air, and a real power meter on the cranks will read a little higher.
  • Mixing up CdA and Cd. The input is drag coefficient times frontal area in m² (typically a few tenths), not the dimensionless Cd.

Sources

About this calculator

The total resistance a cyclist has to overcome is the sum of aerodynamic drag, rolling resistance, and gravitational resistance on any climb — a physics-based model of the forces a rider’s power has to overcome. Drivetrain friction losses are not included, so power measured at the pedals will read somewhat higher.

Cyclists and coaches use it to see at what speed aerodynamic drag starts to dominate (typically above roughly 20–25 km/h) versus when gravity takes over on a climb, which directly informs equipment choices like aero wheels versus a lightweight climbing setup.

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