Tools you might need next
Calculate bicycle gear ratios, gear inches, and development for any chainring and cassette cog combination on your bike.
Find the correct bicycle frame size from inseam, height, and riding style for road, mountain, hybrid, and gravel bicycles.
Calculate bicycle spoke length from hub flange diameter, rim ERD, lacing pattern, and number of crosses for wheel building.
Power to overcome gravity rises with total mass, gradient, and speed.
P_gravity = mass × g × speed × sin(gradient angle)Tires and road surface create a force proportional to weight and rolling coefficient Crr.
P_roll = mass × g × Crr × speedAir resistance dominates on flats and descents. It scales with speed cubed, frontal area, and CdA.
P_aero = 0.5 × ρ × CdA × v³Updated: July 2026
Use known grade and speed on a 10-minute hill when you lack a power meter.
See extra watts needed to hold 22 mph into a headwind at the front.
Compare human-only watt estimate to motor assist level on the same hill.
Percent grade is rise/run × 100. Convert to angle or use established climb power formulas consistently.
Even 5 mph headwind materially increases watts at 20+ mph road speeds.
Estimate how many watts you produce on a climb or flat road. Enter speed, gradient, weight, and wind to approximate power without a meter.