Puerto de Astún

Overview

Puerto de Astún is a Category 1 climb that asks for patience over 14.1 km. From a start elevation of 841 m, the road works its way up to a summit at 1707 m — a net gain of 866 m at an average gradient of 6.16%. That average tells most of the story: this is a long, steady effort rather than a wall-and-recover puzzle. There is one distinct spike, a maximum gradient of 10.79%, but for the majority of the climb you are looking at grades hovering close to the mean. With a total ascent of 840 m recorded over the route, the profile is almost relentlessly upward, with little in the way of false flats or descents to break the rhythm.

How the Gradient Unfolds

The defining feature of Astún is consistency. An average of 6.16% held across 14.1 km means there is nowhere to properly hide — no long plateau to spin out the legs, no extended descent to bank recovery. The gap between the 6.16% average and the 10.79% maximum is modest by mountain standards, which tells you the hardest ramp is not dramatically steeper than the sustained middle. Expect the road to sit in the 5–7% band for long stretches, with the steepest section demanding a brief, deliberate change of gear rather than a full-blown survival scramble. Because net gain (866 m) and total ascent (840 m) are so close, the climb rarely gives elevation back — nearly every metre you earn stays earned.

Pacing Notes

On a climb this evenly graded, pacing is everything. The temptation is to attack the lower slopes while the legs feel fresh, but 14.1 km at 6.16% punishes early enthusiasm. Anchor your effort to a percentage of your FTP and hold it — treating the climb as a single sustained tempo-to-threshold block will serve you far better than surging. If you are unsure of your threshold power, run the numbers through the FTP estimator before you set a target. Save a little in reserve for the 10.79% pitch; when it arrives, lift your effort briefly and settle straight back into rhythm rather than overcooking it. The final drag toward 1707 m is where an honest, well-judged pace pays off.

Gearing

For a Category 1 climb of this length and steadiness, a compact setup is the sensible foundation. A 34×32 will handle the bulk of the 6.16% grade comfortably for most trained riders, letting you keep a smooth cadence over the long middle. If you tend to grind, or you want extra margin for the 10.79% ramp near your limit late in the climb, step up to a 34×34. The extra sprocket costs little and buys real insurance across 14.1 km of continuous ascent — better to spin an easy gear you do not fully need than to be over-geared as the summit approaches.

Summary

Puerto de Astún rewards riders who respect the average and pace with discipline. It is a long, honest Category 1 climb: steady gradients, one meaningful spike, and almost no relief until you reach the top.

Length: 14.1 km
Average gradient: 6.16%
Max gradient: 10.79%
Start: 841 m
Summit: 1707 m
Net gain: 866 m
Total ascent: 840 m
Category: 1