Mont Cenis Pass

Overview

Mont Cenis Pass is a genuine hors catégorie (HC) climb — the hardest rung on the road-cycling ladder, sitting above categories 1 through 4. Over 22.3 km it drags you from a valley floor at 505 m all the way to a 2096 m summit, a net elevation gain of 1591 m. The average gradient of 7.12% never really lets up, and the total ascent of 1568 m confirms that this is close to relentless uphill rather than a climb broken up by descents. Put simply: this is a long, high, sustained effort where the altitude at the top matters as much as the raw metres you climb.

How the Gradient Unfolds

At 22.3 km with a 7.12% average, the defining feature here is duration. This is not a punchy wall — it is a climb you settle into for well over an hour for most riders. But the numbers hide some variation: with a maximum gradient of 12.95%, there are pitches that spike well above the average, nearly double the mean slope in the steepest sections. Expect the road to hover around that 7% figure for long stretches and then bite harder on the ramps. Because the net gain (1591 m) exceeds the total ascent figure convention would suggest a steady grind, the smart read is to treat the whole 22.3 km as one continuous effort and save something for the double-digit pitches rather than burning matches early.

Pacing Notes

On a climb this long, pacing is everything. The single biggest mistake is going out too hard in the first few kilometres while your legs feel fresh. Anchor your effort to your FTP and aim to hold a sustainable percentage of it for the full 22.3 km rather than chasing a number on the steep ramps. When the gradient jumps toward 12.95%, let your speed drop and protect your effort — surging on those pitches costs far more than it gains over an ascent of 1591 m.

If you are not sure what your threshold is, run the numbers through the FTP estimator before you plan your attempt. Knowing that figure lets you pick a target power you can actually defend from 505 m all the way to 2096 m, where thinning air at altitude will quietly sap whatever margin you left yourself.

Gearing

For an HC climb of 22.3 km averaging 7.12% with ramps to 12.95%, gear low and gear early. A compact chainring paired with a wide cassette is the right call for most riders. A 34×32 will get many stronger climbers up the sustained sections comfortably, but given the length and the 12.95% pitches near the top, a 34×34 gives you an extra bailout gear for the steepest ramps and for the moments when altitude blunts your power. If you can fit it, the 34×34 is the safer choice on a climb this long — spinning a low gear preserves your legs across all 1591 m of gain far better than grinding.

Summary

Mont Cenis Pass is a complete HC test: long, high, and steady, with just enough steep pitches to punish poor pacing. Respect the distance, gear low, and meter your effort from bottom to top.

Length — 22.3 km
Average gradient — 7.12%
Max gradient — 12.95%
Start — 505 m
Summit — 2096 m
Net gain — 1591 m
Total ascent — 1568 m
Category — HC