Col de Bouaz

Overview

The Col de Bouaz is not a climb you talk your way through — it is one you survive. Rated hors catégorie (HC), the hardest classification above categories 1 through 4, it stretches 11.9 km and averages a merciless 13.7%. To put that in context, most riders consider anything over 10% "steep." This climb holds nearly 14% as its average, meaning the easy sections are still hard and the hard sections are barely rideable.

Beginning at 389 m and topping out at 2023 m, the road delivers 1634 m of net elevation gain, with 1582 m of total ascent along the way. That difference tells you the profile barely relents — there is almost no descending or false-flat recovery baked into the route. It simply goes up, and it does so with intent.

How the Gradient Unfolds

With an average of 13.7% sustained over 11.9 km, the Col de Bouaz offers no meaningful truce. The number that defines its character, though, is the maximum: 28.41%. A pitch that steep is closer to a wall than a road, the kind of gradient where staying seated becomes physically impossible and traction itself is a question.

Because net gain (1634 m) and total ascent (1582 m) sit so close together, you can read the shape clearly: this is a relentlessly upward climb with negligible respite. Expect the steepest ramps to spike well above the average, dragging you toward that 28.41% ceiling, before settling back into gradients that would headline most other climbs. There is no plateau to spin out your legs and no long shallow run-in — you are climbing hard from bottom to top.

Pacing Notes

On a climb this severe, pacing is everything, and it starts with knowing your FTP. Over 11.9 km at 13.7%, most riders will spend the entire effort at or near threshold simply to keep moving — there is no soft-pedalling a 13.7% average. If you do not know your threshold number, run it through the FTP estimator before you commit.

The tactical trap here is the max-gradient sections. Burning matches to muscle over a 28.41% ramp can spike your effort so far past threshold that you never recover on the (still-brutal) slopes above. Meter your power, protect your cadence, and treat the whole 2023 m summit as the finish line — not the next steep pitch.

Gearing

Do not under-gear this climb. A 13.7% average with 28.41% spikes will punish anything ambitious. A 34×32 is the sensible minimum, and even then you will be grinding on the steepest ramps. For most riders, a 34×34 is the smarter choice — that extra sprocket buys you cadence and keeps your knees intact across the worst pitches toward 2023 m.

If your bike accepts an even easier ratio than 34×34, use it. On a climb gaining 1634 m at these gradients, there is no glory in over-gearing — only survival in spinning.

Summary

The Col de Bouaz is a genuine HC test: short by grand-tour standards at 11.9 km, but savage in gradient, averaging 13.7% with a 28.41% maximum. From 389 m to 2023 m, it climbs 1634 m net with barely a break. Gear low, pace to threshold, and respect every ramp.

Length: 11.9 km
Average gradient: 13.7%
Max gradient: 28.41%
Start: 389 m
Summit: 2023 m
Net gain: 1634 m
Total ascent: 1582 m
Category: HC