How accurate is this estimate?

It is accurate for steady-state climbing in still air. Wind, variable gradient, fatigue and road surface will all affect actual times. Expect real times to be 5-15% slower.

What power should I use?

Use the power you can sustain for the expected duration. For climbs under 20 minutes, use about 105% of FTP. For 30-60 minute climbs, use FTP. For longer, use 85-95% of FTP.

Does this account for descents?

No, this calculates time for a continuous ascent. For routes with mixed terrain, break them into segments or use the Ride Time Calculator.

BikeCalcs

Ascent Time Calculator — Estimate Climbing Time

Estimate climbing time from power, weight and gradient.

Power Output

Sustainable crank power for the climb's duration (≈FTP for 30–60 min climbs)

Total Weight (rider + bike)

Combined rider + bike + kit + bottles weight

Average Gradient

Average slope as rise/run percentage (e.g. 8 for an 8% climb)

Distance

Length of the climb along the road

Crr

Rolling resistance coefficient (~0.004–0.006 for road tyres on tarmac)

CdA

Frontal drag area in m² (~0.30–0.40 seated climbing; aero matters little at climbing speeds)

How We Calculate This

Ascent Time Estimation

Based on the Martin et al. (1998) road-cycling power model, the calculator solves for the steady-state speed at which your power output balances the forces resisting the climb:

P × η = P_gravity + P_rolling + P_aero, where η ≈ 0.976 is the drivetrain efficiency (a clean chain loses ~2.4% before the wheel)
P_gravity = m · g · gradient · v (the dominant term on a climb)
P_rolling = Crr · m · g · v
P_aero = ½ · ρ · CdA · v³ (small at low climbing speeds)
Time = Distance / Speed
VAM = Elevation Gain / Time (in hours) — vertical metres climbed per hour

Frequently Asked Questions

Related Calculators

Climbing Category Calculator

Classify a climb by its category based on length and gradient.

Route Gradient Calculator

Calculate gradient percentage from elevation and distance data.

Elevation Gain Calculator

Calculate total elevation gain from gradient and distance.

Descent Speed Calculator

Estimate safe descent speed based on gradient and conditions.

Wind Effect Calculator

Calculate the impact of wind on speed and power requirements.

Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.