Passo del Miller

Overview

Passo del Miller is an hors catégorie (HC) climb, the hardest classification on the scale before you drop back to categories 1 through 4. Everything about its profile earns that label. Over 20.2 km the road drags you from a start elevation of 418 m up to a 2107 m summit, a net gain of 1689 m. The average gradient sits at a relentless 8.36%, and at its worst the road pitches up to a savage 29.33%. This is not a climb you drift up; it is one you survive.

The total ascent of 1679 m tells you the road climbs almost continuously, with only the faintest respite along the way. At more than 20 km in length and holding an 8%-plus average the whole distance, the Miller belongs in the small club of climbs that reward preparation and punish improvisation.

How the Gradient Unfolds

An 8.36% average across 20.2 km is deceptive on paper. Averages hide the spikes, and here the spikes are extreme: that 29.33% maximum is roughly three and a half times the average gradient. Expect long sustained stretches near the mean, punctuated by ramps that briefly detonate into double-digit and even near-30% walls.

With 1689 m of net gain spread over the distance, roughly 84 vertical metres are earned per kilometre on average. The gap between net gain (1689 m) and total ascent (1679 m) is tiny, confirming there are essentially no descents to recover on. Once you start climbing, you keep climbing.

Pacing Notes

On a climb this long, discipline beats bravado. Set an effort you can hold for well over an hour and defend it. Your FTP is the anchor here: pace the sustained sections at a percentage of it you know you can sustain, and treat the steep ramps as brief surges rather than new baselines. If you don't know your number, run the FTP estimator before you go, then build your climbing power targets around it.

The danger on the Miller is spending too much on early ramps and paying for it across the back half. With 20.2 km to cover and a 2107 m summit, the last kilometres at altitude will feel far harder than the first. Ride the early gradient conservatively and keep something for the top.

Gearing

Gear for the 29.33% max, not the 8.36% average. On a climb of this severity, most riders will want a compact chainset paired with a wide-range cassette. A 34×32 is a sensible floor for strong climbers, but on a 20.2 km HC ascent with near-30% ramps, a 34×34 gives you the extra margin to keep spinning when the road stands up. If your bike accepts it, err toward the easier ratio — the ability to keep cadence over 1689 m of climbing saves your legs for the summit.

Summary

Passo del Miller is a full-length HC test: over 20 km of climbing at more than 8% average, with ramps that hit nearly 30% and a summit above 2100 m. Pace it with your FTP, gear it for the steepest wall, and respect the distance.

Length: 20.2 km
Average gradient: 8.36%
Max gradient: 29.33%
Start: 418 m
Summit: 2107 m
Net gain: 1689 m
Total ascent: 1679 m
Category: HC