Why is aerodynamic power included on a climb?

Many riders assume climbing is only about weight. On steep slow climbs that is mostly true, but on fast shallow climbs the speed is high enough that aerodynamic drag still matters. Because aero power rises with speed cubed, a small increase in speed can require a large increase in power.

What CdA should I use?

A relaxed upright road position may be around 0.35 to 0.45, while a more aerodynamic position may be lower. The exact value depends on rider size, clothing, bike setup, and position. If you do not know your CdA, use the default as a rough estimate.

Does weight matter more than power?

Climbing performance depends on both. Total power determines how much work you can do, and total system weight determines how much work is needed to gain elevation. That is why watts per kilogram is a useful climbing metric, but it is not the only metric on flatter terrain.

Sports & Fitness

Cycling Power To Climb Calculator

Estimate the cycling power needed to climb at a target speed using rider weight, bike weight, gradient, rolling resistance, and aerodynamic assumptions. This tool is built for practical cycling planning, so it includes the core calculation plus supporting outputs, step-by-step explanation, examples, and guidance for real-world riding conditions.

A practical cycling power model

This calculator combines gravity, rolling resistance, and aerodynamic drag. On steep climbs, gravity is usually the largest part. On shallow and fast climbs, aerodynamic drag can become surprisingly important. For a deeper mathematical view of how slope, cadence, gearing, and climbing power interact, see the technical paper on maximizing VAM for a given power.

Formula components

Gravity power ≈ mass × g × speed × sin(slope angle) Rolling power ≈ mass × g × speed × Crr Aero power ≈ 0.5 × air density × CdA × speed³

The final output divides by drivetrain efficiency so the estimated power is closer to what the rider must produce at the crank.

When this calculator is most useful

Use it to compare how much power is needed for a climb, how weight changes affect climbing, or how tire choice and position affect total demand. It is not a race predictor by itself because pacing, heat, altitude, wind, and fatigue matter.

Frequently asked questions

Many riders assume climbing is only about weight. On steep slow climbs that is mostly true, but on fast shallow climbs the speed is high enough that aerodynamic drag still matters. Because aero power rises with speed cubed, a small increase in speed can require a large increase in power.
A relaxed upright road position may be around 0.35 to 0.45, while a more aerodynamic position may be lower. The exact value depends on rider size, clothing, bike setup, and position. If you do not know your CdA, use the default as a rough estimate.
Climbing performance depends on both. Total power determines how much work you can do, and total system weight determines how much work is needed to gain elevation. That is why watts per kilogram is a useful climbing metric, but it is not the only metric on flatter terrain.