Doi Ang Khang

Overview

Doi Ang Khang is a hors catégorie climb that earns its rating the hard way. Over 15 km the road lifts you from 529 m at the base to 1810 m at the summit, a net gain of 1281 m at an average gradient of 8.56%. That average alone would make this a serious effort, but the number that defines the climb is the maximum: 19.45%. This is not a climb you settle into and forget — it is 15 km of sustained, near-double-digit work with ramps that spike into leg-breaking territory. With 1321 m of total ascent logged across the route, there is barely any relief to bank recovery.

How the Gradient Unfolds

The gap between the 8.56% average and the 19.45% maximum tells the story of this climb's shape. An average this high already means the road rarely eases below a hard grind, and the 19.45% pitches sit more than 10 points above that average — the kind of walls that force you out of the saddle and shatter any rhythm you have built. Because the net gain (1281 m) is only slightly below the total ascent (1321 m), there is almost no descending or flat to interrupt the climb. Roughly 40 m of the ascent is spent re-climbing small dips; everything else is up. Expect the steepest ramps to arrive without warning and to demand a deliberate change of gear and posture each time.

Pacing Notes

On a climb averaging 8.56% for 15 km, discipline early is everything. The overwhelming instinct is to attack the first kilometres while the legs feel fresh, but with 1281 m still to gain you will pay for every premature match burned. Anchor your effort to your sustainable power. If you know your FTP, aim to hold just below it on the steady sections so you have headroom for the 19.45% ramps, where power inevitably spikes. If you do not have a current number, run through the FTP estimator before you go — pacing a 15 km HC climb blind is how good days turn into walks. Break the climb into thirds and treat the final third as the one where you are allowed to hurt.

Gearing

Do not under-gear this one. For a 15 km climb averaging 8.56% and touching 19.45%, most riders will want a compact crankset paired with a wide cassette. A 34×32 is the sensible floor, and it will get many strong climbers to the top — but on the 19.45% ramps at the tail of a 1281 m ascent, that ratio can leave you grinding at a cadence that torches your legs. If your bike can take it, a 34×34 gives you the extra spin to keep the pedals turning through the steepest pitches without stalling. When in doubt on an HC climb, choose the easier gear.

Summary

Doi Ang Khang is a pure HC test: long, steep, and unrelenting from 529 m to 1810 m. Gear low, pace honestly, and respect the 19.45% ramps and you will reach the top having earned every metre of the 1281 m gain.

Length: 15 km
Average gradient: 8.56%
Max gradient: 19.45%
Start: 529 m
Summit: 1810 m
Net gain: 1281 m
Total ascent: 1321 m
Category: HC