Col de Champex

Overview

Col de Champex is a genuine hors catégorie test, the kind of climb that leaves no room for a soft opening. Over 12.6 km it averages 8.08%, and that average is the important word here: this is not a climb with long flats hiding brutal walls. The gradient sits high and stays high. You begin at 484 m and finish at 1504 m, a summit elevation gain of 1020 m, with 998 m of total ascent packed into a single sustained effort.

An HC rating is the hardest label a climb can carry, sitting above categories 1 through 4. Champex earns it through length and steepness working together — neither number alone is extreme, but combined across 12.6 km they add up to well over an hour of climbing for most riders.

How the Gradient Unfolds

The defining feature is consistency. At 8.08% average across the full 12.6 km, there is nowhere to truly recover. The maximum pitch reaches 18.87%, more than double the average, so expect ramps that spike hard before settling back toward that punishing baseline.

Do the arithmetic and the shape becomes clear: 1020 m of net gain over 12.6 km is a lot of vertical for the distance. With total ascent at 998 m, the climb runs essentially uphill the entire way, without meaningful descents to reset your legs. Treat every steep section as a moment to survive, not attack, and save something for the fact that the gradient rarely relents before the 1504 m summit.

Pacing Notes

On a climb this long and steady, pacing is everything. Ride the first third comfortably below threshold — the 8.08% average will punish anyone who goes out hard. Your FTP is the number to anchor to: aim to sit just under it on the sustained sections and accept short surges above it only on the 18.87% ramps, where staying seated and spinning is often impossible.

If you don't know your threshold, run the numbers through the FTP estimator before you commit to a target. Knowing that figure turns a guessing game into a plan, and on a 12.6 km HC climb a plan is the difference between reaching 1504 m strong and blowing up two-thirds of the way up.

Gearing

Gear for the average, then gear again for the spikes. With a sustained 8.08% and pitches touching 18.87%, most riders will want the lowest ratio they can run. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible floor for strong climbers, giving you a bailout on the steepest ramps.

If you weigh more, ride at a steady endurance level, or simply want to protect your knees over 1020 m of climbing, step up to 34×34. That extra sprocket keeps your cadence higher on the 18.87% sections and lets you ration effort rather than grind. On an HC climb, under-gearing is a mistake you feel for the entire back half.

Summary

Col de Champex is a long, steep, unrelenting HC climb that rewards patience and honest pacing. Anchor to your threshold, gear low, and respect the fact that 8.08% sustained over 12.6 km leaves nowhere to hide.

Length: 12.6 km
Average gradient: 8.08%
Max gradient: 18.87%
Start: 484 m
Summit: 1504 m
Net gain: 1020 m
Total ascent: 998 m
Category: HC