Climbing Category Calculator — Classify Your Climb

Climbs are rated from Category 4 (easiest) through Category 1 to Hors Catégorie (HC, beyond category). The rating considers both length and steepness.

HC climbs are typically long and steep — generally over 15 km at 7%+ average gradient, or shorter but extremely steep (e.g. 10 km at 10%+).

The difficulty score = length (km) × gradient² (%), the formula used by Tour de France organiser ASO. Score thresholds: Cat 4 under 75, Cat 3 from 75, Cat 2 from 150, Cat 1 from 300, and HC at 600 and above. Squaring the gradient weights steepness more heavily than length, reflecting the physiological reality that steeper climbs are disproportionately harder.

They use the same ASO scoring formula and thresholds (HC 600+, Cat 1 300+, Cat 2 150+, Cat 3 75+). For example, Alpe d’Huez at 13.8 km and 8.1% scores 13.8 × 8.1² ≈ 905, well into HC. Real race classifications can also nudge a climb up a category based on its position in the stage, road surface and other factors, so treat this as a close general guide.