Free Tool
CLIMBING TIME ESTIMATOR
Power, weight, gradient, and distance in. Estimated climbing time, average speed, and VAM out.
FAMOUS CLIMBS — QUICK FILL
Bike, shoes, bottles, kit — everything except you
METHODOLOGY
Physics model: The estimator solves the standard cycling power equation — the same model used by Best Bike Split and race-simulation tools. Total power equals the sum of gravity, aerodynamic drag, and rolling resistance, all multiplied by speed and divided by drivetrain efficiency:
P = (m·g·sinθ·v + ½·ρ·CdA·vair²·v + Crr·m·g·cosθ·v) / η
Solving for speed: Given your power output, the calculator uses Newton-Raphson iteration to find the speed that satisfies the power equation. This converges in a handful of steps and gives the same result as the analytic solution on steep gradients where gravity dominates.
Default assumptions:CdA = 0.35 m² (climbing position on the hoods), Crr= 0.005 (standard road surface), drivetrain efficiency = 97%. Air density starts at 1.225 kg/m³ at sea level and is adjusted for altitude using the International Standard Atmosphere barometric formula — roughly 12% less dense per 1,000 m of elevation.
Wind:Headwind is added to the rider's ground speed when calculating aerodynamic drag. On steep climbs where speeds are low, wind has a disproportionately large effect — a 15 km/h headwind at 12 km/h climbing speed nearly doubles your aero drag.
Limitations: The model assumes constant gradient and steady-state power. Real climbs have variable gradient, switchbacks, and micro-descents that make actual times differ by 2-5% from the estimate. Temperature, road surface, tyre choice, and drafting are not modelled. Treat the output as a planning estimate, not a prediction.
For a deeper look at VAM and how vertical speed relates to climbing ability, see the VAM and climbing speed explainer.
Last updated: July 2026 · Tool version 1.0