How long will this climb actually take?
Predict your time up any mountain from distance, gradient, weight, and sustained power. Works for Strava segments, local climbs, and the famous alpine passes: complete with VAM and W/kg benchmarks.
P = m·g·(sinθ + Crr·cosθ)·v + ½·CdA·ρ·v³. A fit amateur at 3.5 W/kg climbs Alpe d'Huez (13.8 km, 8.1%) in ~58 min.Enter your climb
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Track actual climb times and compare to this calculator's predictions. Built-in climb detection and VAM display.
How the bike climb calculator works
The calculator solves the standard cycling power equation for velocity, then divides distance by that velocity to get time. The equation balances three forces that resist your forward motion on a climb:
- Gravity-
m·g·sin(θ)·v: dominates on gradients over 5%. This is why weight matters so much on climbs. - Rolling resistance-
Crr·m·g·cos(θ)·v: depends on tire, pavement, and pressure. Fast road tires have Crr around 0.004. - Aerodynamic drag-
½·CdA·ρ·v³: scales with the cube of velocity. Above ~25 km/h it becomes a meaningful drag; below that it's tiny.
For steep climbs at low speeds, gravity is typically 80-95% of total resistance. For shallow climbs (under 3%) at higher speeds, aero becomes the main factor, which is why positioning and gear selection can matter even on modest gradients.
Understanding VAM (Velocità Ascensionale Media)
VAM is vertical meters climbed per hour, the single best metric for comparing climbing performance across different gradients and distances. Benchmarks:
- Casual rider: 600-900 m/h
- Fit amateur: 900-1,200 m/h
- Strong amateur / cat 3: 1,200-1,500 m/h
- Elite amateur: 1,500-1,700 m/h
- Professional: 1,700-1,900+ m/h on signature climbs
Why total mass matters more than you think
On an 8% climb at FTP, roughly 85% of your power fights gravity. A 1 kg reduction in bike+rider mass saves about 1% of climb time. That's about 34 seconds over an hour-long climb. Before spending $3,000 on a lighter frame, consider: losing 1 kg from the rider is free and equally effective.
Choosing the right power number
The calculator is only as accurate as the power you enter. Use:
- Your FTP for climbs between 20 and 60 minutes.
- 20-minute power (about 1.05× FTP) for sub-20-minute climbs.
- 85-90% of FTP for climbs lasting 1-2 hours.
- 75-85% of FTP for multi-hour efforts (Tour-stage style).
Don't know your FTP? Run our FTP Calculator first. Need training zones? Try the Heart Rate Zone Calculator.
Frequently Asked Questions
5 QuestionsHow accurate is this calculator?
Within 3-5% for steady-state climbs on dry pavement in calm conditions. Accuracy drops with variable gradients, switchbacks, wind, and changes in rider pacing. The calculator assumes constant power, which real climbs rarely match exactly.
Does wind affect the result?
Not in this version, the model uses still-air aerodynamics. For steep climbs (over 7%) at climbing speeds, wind has minimal effect. On shallower climbs at higher speeds, headwinds can add 10-30 seconds per km.
What is a good W/kg for climbing?
2.0-2.5 W/kg is fitness-level, 3.0-3.5 is solid amateur, 4.0+ is competitive racer, 5.0+ is elite, 6.0+ is pro. Climbing speed scales linearly with W/kg on steep gradients.
How long does Alpe d'Huez take?
At 3.0 W/kg: ~68 min. At 3.5 W/kg: ~58 min. At 4.0 W/kg: ~51 min. At 5.0 W/kg: ~42 min. The pro record (Pantani, 1997) is 37:35 at an estimated 6.5 W/kg.
Can I use this for Zwift climbs?
Yes: Zwift uses the same physics model, so predictions are very accurate on Zwift. The main variable is trainer power smoothing and whether you hold steady power or punch above on steeper sections.
Frequently Asked Questions
How is bike climb time calculated?
Climb time is derived from the power equation: P = m·g·(sinθ + Crr·cosθ)·v + 0.5·CdA·ρ·v³, solved for velocity given your sustained power, total mass, gradient, rolling resistance, and aerodynamic drag. Time equals distance divided by that velocity.
What is VAM in cycling?
VAM stands for 'Velocità Ascensionale Media', the rate of vertical ascent in meters per hour. A VAM above 1,000 m/h is strong, 1,400+ m/h is pro-level, and elite climbers sustain 1,700+ m/h on long alpine climbs.
How long does it take to climb Alpe d'Huez?
Alpe d'Huez is 13.8 km at an average 8.1% gradient. A fit amateur at 3.5 W/kg can expect 55-65 minutes. Top amateurs climb it in 45-50 minutes (4.2-4.5 W/kg). The pro record is 37:35 by Marco Pantani.
Does bike weight really matter on climbs?
On steep climbs (over 6%), gravity dominates drag, so every extra pound costs time. Saving 1 kg on an 8% climb roughly saves 1% of your climb time at the same wattage. On shallower climbs, aerodynamics matter more.
What power should I use, FTP or something lower?
For climbs under 20 minutes, use your 20-minute power (slightly above FTP). For 20-60 minute climbs, use FTP (about 95% of 20-min power). For climbs over an hour, use 85-90% of FTP, that's sustainable for most trained riders.
What power should I use, FTP or something lower?
For climbs under 20 minutes, use your 20-minute power (slightly above FTP). For 20-60 minute climbs, use FTP (about 95% of 20-min power). For climbs over an hour, use 85-90% of FTP, that's sustainable for most trained riders.
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