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PaceCalc
How many watts does that speed cost?
Aerodynamic power scales with velocity cubed, so going from 30 to 40 km/h on the flat does not need 33% more power — it needs well over twice as much. This is why aero position and equipment matter enormously at racing speeds and barely at all when climbing slowly.
On a steep gradient almost all your power goes into lifting mass against gravity, and that term scales directly with total weight. Riders are compared by W/kg rather than raw watts because a 60 kg climber at 300 W out-climbs an 85 kg rider at the same output.
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OpenLast updated: August 2026
Power Required
143 W
What you entered
Convert speed to m/s
30 / 3.6= 8.3333 m/sRolling resistance power
0.005 x 83 kg x 9.8067 x cos(slope) x 8.3333= 33.9148 WClimbing power
83 kg x 9.8067 x sin(atan(0/100)) x 8.3333= 0 WAerodynamic drag power
0.5 x 1.225 x 0.3 x 8.3333^3= 106.3368 WTotal at the pedals (after drivetrain loss)
(33.9148 + 0 + 106.3368) / (1 - 2/100)= 143.1139 WResult
Power Required: 143 W
Holding 30 km/h on a 0% gradient takes about 143 W, or 1.91 W/kg.