Col du Portillon: Cycling Climb

The climb · France

About Col du Portillon

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Simon Warren’s 100 Greatest Cycling Climbs of the Tour de France

A classic climb with a mix of forest and open sections. Gradients rise fairly, with occasional sharper sections to remind legs of effort. By the top, the mountain air and quiet roads feel like a reward.

01 / The ascent

Elevation profile

Start 688 m · Summit 1,297 m

Gradient by distance7.85 km / 617 m gain

0 km1.6 km3.1 km4.7 km6.3 km7.8 km

02 / The crux

Where it gets difficult

Choose a distance to find the steepest continuous section of the climb.

Steepest 500 m average

10.9%

Where to find it

2.50–3.00 km from start

Net height gained: 55 m
Section length: 500 m

The whole climb7.85 km

0 kmFinish

03 / The numbers

Climb statistics

Distance: 7.85 km
Elevation gain: 617 m
Average gradient: 7.7%
Climb category: 2
Start elevation: 688 m
Summit elevation: 1,297 m

Current weather

At the climb start

Loading weather…

Weather data: MET Norway

04 / Your effort

How long would it take?

Enter the power you could hold for the whole climb. We calculate a moving time from the elevation profile and the forces you ride against.

Sustained power

W/kg

Use your intended climbing effort, rather than FTP unless you can hold it for the predicted duration.

Rider weight (kg)

Bike + kit weight (kg)

Bike + kit includes clothing, bottles and luggage.

Advanced settings

Defaults represent a road-bike scenario. Adjust these settings to match your tyres, drivetrain and riding position.

Effective drag area (CdA) (m²)

Rolling resistance (Crr)

Drivetrain efficiency (%)

Modelled moving time

41 min

Power throughout: 225 W
Average speed: 11.4 km/h

Based on the 7.85 km elevation profile. Assumes steady power, with no stops, braking or drafting. Rounded to the nearest minute.

The science behind the calculation

For each part of the stored profile, we solve the steady-state cycling power equation for speed, then add distance ÷ speed across the climb. Gravity uses rider + equipment weight; available power is W/kg × rider weight. This uses the profile’s distance and elevation together, without mixing in another route’s metrics.

Power × efficiency = gravity + rolling resistance + air resistance + bearing losses

The resistance equations are adapted from Martin et al. (1998), Validation of a Mathematical Model for Road Cycling Power. Air density changes with profile altitude using NASA’s standard-atmosphere model. This calculator’s adaptation has not been independently validated.

It predicts travel at the power you enter, including on descents. It does not model acceleration, cornering, braking, traffic, wind, changing weather or fatigue. At altitude, choose power you can sustain there: thinner air reduces drag, but this model does not predict its effect on your ability to produce power. Profile quality and assumed equipment settings also affect the result.

05 / On the ground