The Hors Catégorie / Cat 1-4 system used by Tour organisers is a categorisation, not a difficulty prediction. Two climbs rated the same can be radically different on the bike. This calculator adds a time estimate at your W/kg, a gradient profile, and a "compared to known climbs" panel.
| Climb | Length | Avg % | Top m | Similarity |
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The UCI Hors Catégorie 1-5 scale is based purely on length and average gradient, with the magic formula: difficulty = (length in km × avg gradient²). It's a quick way for race organisers to label climbs for the roadbook. It tells you nothing about how a climb will feel.
Two Cat 1 climbs can have totally different profiles: a steady 7% over 12 km, or a 9% average with 15% ramps in the middle. The first is a tempo climb; the second is a leg-breaker. Our calculator surfaces both the official category and what it'll feel like on the bike.
The Tour category formula ignores altitude, gradient variability and surface. A Cat 2 at 2000 m with bad pavement is harder than a Cat 1 at sea level on smooth tarmac. Use the time prediction, not the category, to plan.
Most cycling computers and apps (Strava, Komoot, RideWithGPS) export a climb-by-climb profile. Or use a free tool like GPX.studio to plot a route and read the gradient distribution.
Two reasons are most common: (1) you held higher than FTP — fine, you're stronger than you thought; (2) you faded in the back third — pacing is too aggressive. Either way, use the result to plan, not to grade yourself.
This calculator was built to answer a question most online versions skip or oversimplify. It runs entirely in your browser; no inputs are stored or transmitted. The math is grounded in standard cycling physics and physiology models, and is suitable for hobbyist and intermediate training use. It is not a substitute for a coach, sports scientist, or professional bike-fit service.
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Children under 13 are not the intended audience.
This calculator is provided for general informational and educational purposes only. It is not medical, mechanical, or legal advice. Predicted values depend on inputs you supply and simplified physical models; real-world outcomes vary. Use at your own risk. Brand names are descriptive only and do not imply affiliation.