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Cycling Power Calculator

Calculate cycling power output from speed, mass, and grade.

Introduction

Cycling Power Calculator — Calculate cycling power output from speed, mass, and grade. Enter Total mass (rider + bike, kg), Speed (km/h), Grade (%), Rolling resistance (Crr), Drag area (CdA, m²) to get an instant, accurate result.

Formula

Power = (rolling resistance force + aerodynamic drag force + gravity force) × velocity, where rolling force = Crr×m×g×cos(θ), drag force = 0.5×ρ×CdA×v², and gravity force = m×g×sin(θ) (θ from grade %, g = 9.80665 m/s², default air density ρ = 1.225 kg/m³).

Step-by-step

  1. Enter the Total mass (rider + bike, kg).
  2. Enter the Speed (km/h).
  3. Enter the Grade (%).
  4. Enter the Rolling resistance (Crr).
  5. Enter the Drag area (CdA, m²).
  6. Click Calculate to see your result instantly.

Real-world example

Example: With Total mass (rider + bike, kg) = 75 kg, Speed (km/h) = 30 km/h, Grade (%) = 0 %, Rolling resistance (Crr) = 0.005, Drag area (CdA, m²) = 0.3 m², the Cycling Power Calculator gives Power Watts: 136.9826, Rolling Watts: 30.6458, Drag Watts: 106.3368.

Frequently Asked Questions

Why does a small grade change make such a big power difference?
On climbs, the gravity term (m×g×sin(θ)) scales directly with rider+bike weight and grade, and can dominate the other two terms — even a few percent of grade adds substantial power demand.
What is CdA and why does it matter?
CdA is your effective frontal area combined with your aerodynamic drag coefficient. Since aerodynamic drag grows with the square of speed, a lower CdA (an aero position or equipment) has an outsized effect on power needed at higher speeds.
Does this account for drivetrain losses?
No, this is the power delivered at the wheel to overcome rolling resistance, air drag, and gravity — it doesn't add a separate drivetrain efficiency loss on top.
What inputs does the Cycling Power Calculator need?
You'll need to provide: Total mass (rider + bike, kg), Speed (km/h), Grade (%), Rolling resistance (Crr), Drag area (CdA, m²). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Cycling Power Calculator?
The Cycling Power Calculator applies the formula exactly as calculated — Power = (rolling resistance force + aerodynamic drag force + gravity force) × velocity, where rolling force = Crr×m×g×cos(θ), drag force = 0.5×ρ×CdA×v², and gravity force = m×g×sin(θ) (θ from grade %, g = 9.80665 m/s², default air density ρ = 1.225 kg/m³). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Cycling Power Calculator free to use?
Yes, the Cycling Power Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Cycling Power Calculator

The Cycling Power Calculator uses a real, verifiable formula — Power = (rolling resistance force + aerodynamic drag force + gravity force) × velocity, where rolling force = Crr×m×g×cos(θ), drag force = 0.5×ρ×CdA×v², and gravity force = m×g×sin(θ) (θ from grade %, g = 9.80665 m/s², default air density ρ = 1.225 kg/m³). — so results are accurate every time, not an approximation.