🚴 Cycling Power & Speed Calculator

How many watts to hold 40 km/h up a 4% climb? Or what speed does your FTP actually buy you? This models the three forces a rider fights — rolling resistance, air drag and gravity — and splits your power between them, in either direction.

The physics & the approximations

Rolling power = Crr × mass × g × v. Air power = ½ × ρ × CdA × v³ (with headwind added to v). Gravity power = mass × g × v × sin(arctan(grade)). A 2% drivetrain loss is added on top. This is a clean-air, steady-state model: it ignores acceleration, drafting, corners and road surface, so treat the answer as the sustained power a solo rider needs, not an exact watts-per-pedal-stroke.