Col d'Outanne

Overview

The Col d'Outanne is a hors catégorie (HC) climb — the hardest rating in cycling — and the numbers explain why. Over 16.4 km the road gains 1461 m of net elevation at an average gradient of 8.9%, rising from 390 m at the base to a summit at 1851 m. That average alone would qualify most climbs as severe; here it is sustained for the better part of an hour or more. With a maximum pitch of 20.63% and a total ascent of 1408 m, Outanne offers almost nowhere to recover. This is a climb you respect before you ever clip in.

How the Gradient Unfolds

An 8.9% average across 16.4 km tells you the climb rarely dips into easy territory. To hold that mean while touching a maximum of 20.63%, the profile has to stack long stretches at or above 9% between the harshest ramps. The gap between the average and the max — roughly 11.73 percentage points — signals sharp spikes rather than a metronomic drag. The fact that net gain (1461 m) slightly exceeds total ascent (1408 m) confirms there is essentially no false-flat relief or descending recovery inside the climb: every metre gained is a metre climbed. Expect the steepest ramps to punish any rider who arrived with an empty tank.

Pacing Notes

On a climb this long and this steep, discipline beats bravado. Ride to a percentage of your FTP rather than to feel, because the 20.63% ramps will spike your power far above threshold whether you intend it or not. If you do not know your threshold number, run the FTP estimator first and build your target from there. A sensible plan is to settle into a steady sub-threshold effort on the sustained 8.9% sections, then accept short surges above threshold only where the gradient forces it — and immediately settle back down once the pitch eases. Over 16.4 km and 1461 m of climbing, the riders who blow up are almost always the ones who chased the early ramps.

Gearing

Gearing is not a luxury on Outanne — it is survival. With an 8.9% average and a 20.63% maximum, you want the lowest ratios you can comfortably fit. A 34×32 is the sensible floor for strong climbers, but most riders will be far happier on a 34×34, which keeps cadence alive on the steepest pitches and protects your knees across 1408 m of ascent. If your bike accepts anything lower still, use it. Spinning a smaller gear at higher cadence preserves your legs for the full 16.4 km far better than grinding a big gear and torching your reserves early.

Summary

The Col d'Outanne is a genuine HC test: 16.4 km, 8.9% average, and a 20.63% maximum, with 1461 m of net gain to a 1851 m summit and virtually no respite along the way. Pace it by threshold, gear it low, and treat the steepest ramps with caution — do those three things and this monster becomes a triumph rather than a survival story.

Length: 16.4 km
Average gradient: 8.9%
Max gradient: 20.63%
Start: 390 m
Summit: 1851 m
Net gain: 1461 m
Total ascent: 1408 m
Category: HC