Cycling Power Calculator
Estimate the power needed to ride at a speed.
Road slope; default 0
Default 0.4
Results update as you type.
How it works
This calculator estimates the power in watts a cyclist must produce to ride at a given speed, accounting for the three main forces that resist motion. You enter the combined rider and bike weight, the speed, the road gradient, and optionally your aerodynamic drag area, and it returns the required power. The estimate sums three resistances. Rolling resistance comes from the tires deforming on the road and grows with weight and speed. Aerodynamic drag is usually the biggest factor on flat ground and rises with the cube of speed, which is why going faster costs dramatically more power and why aerodynamics matter so much in cycling. The gravitational component appears on climbs, proportional to weight and gradient, and dominates on steep hills where speed is low. The calculator uses standard sea-level air density and a typical rolling-resistance coefficient, with an adjustable drag area to reflect your position and equipment. This is an idealized model that ignores wind, drivetrain losses of a few percent, and acceleration, so real power will be somewhat higher, but it captures the physics well enough to understand trade-offs. Cyclists use it to relate power, speed, and gradient, plan pacing, and see the payoff of losing weight or improving aerodynamics. Enter your weight, speed, and gradient to estimate cycling power.
P = rolling + aero + gravity resistance × speed
The power to ride equals the sum of three resistances, each multiplied by speed: rolling resistance from the tires, aerodynamic drag that rises with the cube of speed, and the gravitational component on a gradient. The calculator uses standard air density and a rolling-resistance coefficient. Aerodynamic drag dominates at higher speeds, while gravity dominates on steep climbs.
Source:Cycling physics
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter rider + bike weight and speed.
- 2
Adjust the options
Adjust gradient and drag area cda if they apply — sensible defaults are already set.
- 3
Read your result
Power required updates instantly as you type — no button to press.
Frequently asked questions
How is cycling power calculated?
Power is the sum of three resistances, each multiplied by speed: rolling resistance from the tires, aerodynamic drag that grows with the cube of speed, and the gravitational force on a gradient. The calculator combines these using standard air density and rolling-resistance values, giving the watts needed to maintain your entered speed.
Why does going faster take so much more power?
Aerodynamic drag rises with the cube of speed, so doubling your speed on flat ground requires roughly eight times the power to overcome air resistance. This cubic relationship is why small speed gains at high speed demand large power increases, and why aerodynamic position and equipment matter enormously in fast cycling.
What is CdA?
CdA is your drag area, the product of the drag coefficient and frontal area, in square meters. It captures how aerodynamic you and your bike are. A lower CdA means less air resistance and less power needed at speed. Typical road-cycling values range from about 0.3 in an aggressive aero position to 0.5 sitting upright.
Why does weight matter more on climbs?
On a gradient, part of your power goes into lifting your combined weight against gravity, and this component is proportional to both weight and steepness. On steep climbs where speed is low, gravity dominates over aerodynamic drag, so losing weight makes a big difference to climbing power, while on flat ground aerodynamics matter far more.
Is this the exact power I need?
It is a close estimate but idealized. It ignores wind, drivetrain friction of a few percent, road surface variation, and the power to accelerate. Real-world power is usually a bit higher than calculated. Use it to understand relationships between power, speed, and gradient rather than as a precise substitute for a power meter.