How are climbs categorised?

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

What makes a climb Hors Catégorie?

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%+).

How does the scoring work?

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.

Are these categories the same as the Tour de France?

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.

BikeCalcs

Climbing Category Calculator — Classify Your Climb

Classify a climb by its category based on length and gradient.

Climb Length

Total distance of the climb from base to summit (not your whole ride)

Average Gradient

Average percentage slope over the whole climb (total rise ÷ run × 100)

How We Calculate This

Climb Classification

Score = Length (km) x Average Gradient (%)²
Cat 4: Score < 75
Cat 3: Score 75-149
Cat 2: Score 150-299
Cat 1: Score 300-599
HC: Score 600+

Frequently Asked Questions

Related Calculators

Route Gradient Calculator

Calculate gradient percentage from elevation and distance data.

Elevation Gain Calculator

Calculate total elevation gain from gradient and distance.

Ascent Time Calculator

Estimate climbing time from power, weight and gradient.

Descent Speed Calculator

Estimate safe descent speed based on gradient and conditions.

Wind Effect Calculator

Calculate the impact of wind on speed and power requirements.

Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.