Col de Mary

Overview

Col de Mary is a hors catégorie (HC) climb, the top rung of the classification ladder above categories 1 through 4, and it earns that rating the hard way. Over 22.3 km the road lifts you from 950 m to a summit of 2608 m, a net gain of 1658 m at an average gradient of 7.45%. The total ascent of 1699 m sits just above the net figure, meaning the profile barely relents once it begins. This is a sustained, high-altitude effort measured in hours, not minutes, and the thin air near the top only sharpens the difficulty already baked into the numbers.

How the Gradient Unfolds

The headline average of 7.45% is honest but deceptive in the way all long HC climbs are: an average is a smoothing of extremes. With a maximum gradient of 15.53%, more than double the mean, there are ramps here that will punch well above what your legs expect from the overall figure. Because total ascent (1699 m) exceeds net gain (1658 m) by only 41 m, there is almost no downhill respite embedded in the climb. You do not get free-rolling recovery sections; nearly every metre gained stays gained. Expect the gradient to oscillate between long stretches near the 7.45% average and sharper double-digit kicks that spike toward 15.53%, with little flat road to reset your rhythm.

Pacing Notes

On a climb of this length, pacing discipline decides your day. Anchor your effort to your FTP: on a 22.3 km ascent you should sit comfortably below threshold on the average pitches, holding a sustainable percentage of FTP so you have headroom left for the ramps toward 15.53%. Blowing up on an early steep section leaves a lot of the 1658 m still to climb. If you don't know your threshold number, run it through the FTP estimator before you plan a target power. The key habit is throttling back on the steep kicks rather than chasing them, then re-settling into rhythm the moment the road eases back toward 7.45%.

Gearing

Come geared for a long grind punctuated by steep bites. On an HC climb averaging 7.45% and spiking to 15.53%, most riders want a compact setup with a wide-range cassette. A 34×32 lowest gear is the practical minimum here, and even strong climbers will appreciate having it in reserve across 22.3 km. If your legs, weight, or the altitude near 2608 m have you worried about the steepest ramps, size up to a 34×34 so you can keep the cranks turning smoothly instead of grinding to a lurching, muscle-shredding cadence on the hardest pitches.

Summary

Col de Mary is a true high-mountain test: long, steep, and unrelenting from base to summit, with 1658 m of net vertical stacked into 22.3 km. Respect the average, plan for the maximum, and gear low enough to protect your rhythm all the way to the top.

Length: 22.3 km
Average gradient: 7.45%
Max gradient: 15.53%
Start: 950 m
Summit: 2608 m
Net gain: 1658 m
Total ascent: 1699 m
Category: HC