Calculate the aerodynamic-drag power cost of a known CdA at a given speed, wind and elevation.
Riding-position CdA values are broad category defaults. Know your own measured CdA instead? Use the CdA Calculator to estimate it from a ride, then enter it here directly.
Aero watts are the portion of total cycling power spent purely overcoming aerodynamic drag — typically the single largest power component at road-riding speeds. This calculator is the forward counterpart to the CdA Calculator: given a known CdA, how many watts does that drag cost at a given speed?
This calculator uses the exact aerodynamic-drag term from this site's physics engine, not a separate formula:
Aero watts is that force multiplied by speed. Air density falls with elevation, which is why the same CdA and speed cost fewer watts at altitude.
Take a rider on the hoods with standard wheels (CdA = 0.324 m²), riding at 25 mph with no wind at sea level:
Enter your own speed, wind and CdA above to see your own number.
Drag force grows with the square of speed, and power grows with the cube of speed — so aero watts rise very quickly as you go faster. This is why small CdA reductions (a lower position, an aero wheelset) are worth disproportionately more watts at race pace than at an easy pace, and why headwinds hurt so much more than tailwinds help by the same ground-speed margin.
Aerodynamic drag scales with the cube of speed; rolling resistance scales linearly. That means aero watts dominate total power at race pace, while rolling resistance is relatively more significant at lower speeds. To see the rolling-resistance side of the comparison, use the Rolling Resistance Calculator, or get the full combined breakdown from the Cycling Watts Calculator.
This calculator reuses the same classical-mechanics drag term documented for the Cycling Watts Calculator and the CdA Calculator (the approach used by Analytic Cycling and similar bike-power calculators) — no new physics model is introduced. It assumes a single scalar wind speed with no yaw-angle modeling, and no drafting.
