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Climb Duel – cycling climb time calculator

Cycling climb time calculator

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What you enter for each rider…
Rider (kg)
Bike (kg)

Replay

Race clock 0:00Gap on the road 0 m

The numbers

GravityRolling resistanceAir drag
Advanced physics (same for both riders)

How it is calculated

η · P = v · [ m·g·(sin θ + Crr·cos θ) + ½·ρ·CdA·v² ]

P is the power at the pedals and η the drivetrain efficiency. Gravity, rolling resistance and air drag are the three forces the rider pushes against, and their sum times speed is the power the wheel must deliver. Solving for v gives the steady climbing speed. Time is the distance along the road divided by v.

  • m is rider plus bike. θ = arctan(grade ÷ 100), so a 6% grade is 3.4°. Distance is measured along the road.
  • Flat-pace mode: the pace you enter is plugged in with θ = 0 to find the power you can hold. That same power is then used on the slope and the cubic is solved for v.
  • Watts mode: the average power you enter at the pedals is used directly on the slope and the cubic is solved for v. With equal watts the heavier rider is slower.
  • Climb-speed mode: the speed is fixed and the equation gives the power it costs. A negative result means gravity does the work and the rider can coast.
  • Not modelled: wind (air speed equals ground speed), standing starts, wheel inertia, drafting, braking and posture changes.

Questions and answers

How does Climb Duel calculate the time to the top?

It balances the rider’s pedalling power against gravity, rolling resistance and air drag, then solves for the steady speed on the slope. Time is the distance along the road divided by that speed.

What does “pace on flat road” mean?

It is the speed a rider holds on level ground. Climb Duel uses it to work out the power that rider can sustain, then applies the same power on the hill. If you know your power or your climbing speed instead, choose “Watts” or “Climb speed”.

Can I enter my power in watts?

Yes. Choose “Watts” and enter the average power each rider pushes at the pedals. Climb Duel then solves the speed on the slope for that power, so weight and grade decide who is faster. The results table also shows watts per kilogram.

Does a lighter bike or a lighter rider matter more on a climb?

Gravity acts on the total mass, so one kilogram less on the bike helps exactly as much as one kilogram less on the rider. What differs is how easy each kilogram is to change. The results table shows the time that one extra kilogram costs each rider.

Does the calculator include wind or drafting?

No. It assumes still air, a steady speed and no drafting, so both riders are compared under the same simple conditions. Real rides also depend on wind, road surface, standing starts and braking.

What are drag area (CdA) and rolling resistance (Crr)?

CdA is the frontal area a rider presents to the air multiplied by a drag coefficient. Crr describes how much the tyres resist rolling. The defaults, 0.32 m² and 0.005, are typical for a road bike on smooth tarmac. Change them under Advanced physics.

How accurate are the results?

They are estimates from the standard steady-state power equation. Accuracy depends on realistic values for drag area (CdA), rolling resistance and drivetrain efficiency, which you can change under Advanced physics.

Why is the slope in the replay steeper than my grade?

The replay exaggerates the slope so that a gentle grade such as 3% is still easy to see. The calculation always uses the exact grade you enter.

Is my data stored or sent anywhere?

No. All calculations run in your browser and nothing you enter leaves your device.