Hors Catégorie, Explained: The Formula Behind Tour de France Climbs
There's no official rulebook for ranking Tour de France mountains — just a race director's formula, a stopwatch's worth of judgment, and a century of arguments over which climbs deserve the honor.
Alpe d'Huez scores 905. Not out of some panel's vote, not off a stopwatch alone, but off a piece of arithmetic that Tour de France race director Thierry Gouvenou punches into a calculator: distance in kilometers times the average gradient, squared. For the Alpe, that's 13.8 times 8.1 times 8.1. Clear the 600 mark and a climb is hors catégorie, literally "beyond category," the top of a five-tier system that has decided who wears cycling's polka-dot jersey since before most of this year's peloton was born.
It matters more than usual right now. Tadej Pogačar leads the 2026 Tour by roughly five minutes over Remco Evenepoel heading into the race's final week, and the queen stage still to come, stage 20 from Le Bourg-d'Oisans, three hors catégorie climbs deep and finishing on Alpe d'Huez, is exactly the kind of day the category system was built to reward. But almost nobody watching that stage could explain why the Col de la Croix de Fer counts as HC while a similar-looking pass twenty miles away gets filed as a category 2. The answer turns out to be part formula, part judgment call, and part marketing.
Where the categories actually come from
Four categories became five in 1979, when Tour organizers decided the existing four-tier system, introduced piecemeal between 1947 and 1962, no longer captured the gap between a hard climb and a genuinely brutal one. Rather than add a numbered fifth tier, they invented hors catégorie: a climb rated as unrankable by the normal scale. Today the ranking runs backward from difficulty. Category 4 is the easiest, category 1 the hardest of the numbered tiers, and HC sits above all of them.
There's a folk story about how the categories were set that Gouvenou hears constantly and doesn't buy.
"Perhaps the story came from a drunken night between journalists. In cycling we have so many stories like that that have been embellished over time. Maybe there's some truth in it somewhere, but I'm not convinced."
Thierry Gouvenou, Tour de France race director, to Rouleur
The story he's dismissing: that categories were once set by which gear a Citroën 2CV needed to crawl up the mountain. It's a nice image, an underpowered postwar car wheezing up a Pyrenean pass and deciding history by its gearbox. It's also, per the man who actually classifies these roads for a living, most likely a myth.
What is the real formula for Tour de France climb categories?
For a climb without an established reputation, Gouvenou's team at ASO, the Tour's organizing body, runs the numbers first and argues about the exceptions second. Essentially, if we have a climb that isn't so well known, we multiply the distance by the average gradient squared,
he told Rouleur. Applied to Alpe d'Huez, 13.8 kilometers long and averaging 8.1%, the sum is 13.8 x (8.1 x 8.1), which comes out to 905. Gouvenou's bands, built by reverse-engineering fifteen years of past classifications and mapped against the mountains classification points system, run like this:
| Score | Category |
|---|---|
| 600 and above | Hors catégorie |
| 300–600 | Category 1 |
| 150–300 | Category 2 |
| 75–150 | Category 3 |
| Up to 75 | Category 4 |
"I applied this to the Tour de France and went back over all the climbs about 15 years ago," Gouvenou said. "As it turned out, most of what had been done over the years fit within this framework. There are exceptions of course, but for the most part, it matched up." The formula isn't published in any race manual. It exists because one man reverse-engineered decades of gut calls and found they were, mostly, defensible math all along.
That last figure belongs to the Col de la Loze, a newly paved Alpine road ASO scouted in 2019 ahead of its 2020 debut. "When we did the recon in the car, we realised we had something exceptional in front of us," Gouvenou said. He ran the numbers and got 1,300, more than double the HC threshold. The Loze now sits alongside the Col du Portet, Mont Ventoux and the Plateau de Beille among the hardest climbs the Tour has ever staged.
Can the same mountain get two different categories?
Yes, and the Col du Galibier is the clearest proof the formula bends to reputation. The pass has two approaches, both used in the 2022 Tour on back-to-back stages. The tougher southern climb from Valloire scored 843, comfortably HC. The gentler route from Briçanon scored 598, two points short of the 600 cutoff, which by the letter of the formula should have made it a category 1 climb instead. ASO kept it HC anyway. First tackled by the Tour in 1911 and topping out at 2,642 meters, the Galibier has more than a century of history behind it, and Gouvenou is candid that legacy carries real weight. "Climbs where there have been great battles, big cycling moments," he said. "That helps us to rank them."
Where a climb sits inside a stage matters too. A mid-pack ascent can get bumped up a category simply for landing near the finish line, where fatigue turns a moderate gradient into a selector. Gouvenou says that mostly applies to the lesser-known climbs rather than the Tourmalets and Ventoux of the world, which keep their rating regardless of placement.
Why do some easy hills get ranked as climbs at all?
Here the math gives way to stagecraft, and it's the part of the system that looks least like engineering and most like a broadcaster building a storyline. When the 2022 Tour opened in Denmark, riders crossed six category 4 climbs before they'd even reached France, bumps that, by Gouvenou's own admission, "barely met the threshold" for classification. ASO ranked them anyway, because the polka-dot competition needs contenders from stage one, and a jersey race with no leader for a week is a jersey race nobody in the broadcast truck wants. "We're not strictly rigid with the classifications," Gouvenou said. "The maths is really just to verify."
The jersey itself is a reminder that this was always partly commercial theater. When the King of the Mountains competition began in 1933, there was no jersey at all, just points: ten for the fastest man over the top, down to one for the tenth. The white shirt with red dots didn't arrive until 1975, and the pattern wasn't chosen for symbolism. It matched the candy wrappers of Chocolat Poulain, the competition's sponsor at the time. Sixty-plus years later, the polka dots are one of cycling's most recognized images, still doing a chocolate company's old marketing job long after most fans have forgotten why.
What counts as an hors catégorie climb today?
Between 2012 and 2016 the average HC climb in the Tour ran 16.1 kilometers at a 7.4% grade, and a typical edition carries around seven of them. This year's route has six, including the Tourmalet's 17.1 kilometers at 7.3% in the Pyrenees and, in the Alps, the Col de la Croix de Fer, the Col du Galibier and the Col de Sarenne all inside a single stage before the road tips down into Alpe d'Huez. It is, by any formula, an absurd stage to put together, and precisely the kind of day ASO's classification system exists to flag in advance, so a rider like Pogačar knows exactly where the race will be won or lost before the flag drops.
Gouvenou's math will keep doing its quiet work long after this year's jersey is decided in Paris. It just won't get the credit the drunken 2CV story does, not yet, anyway.
