The Yosemite Decimal System Explained
Travel to the United States to climb and you will leave French grades behind for the Yosemite Decimal System, or YDS. Born in California's Sierra Nevada in the mid-twentieth century, it is the language of American guidebooks, from the granite of Yosemite to the sandstone of Red Rock. It looks puzzling at first — why does technical rock climbing start at "5.something"? — but its logic is consistent once you learn the structure. Understanding it lets you read North American routes and convert sensibly to the systems you already know. Explore American climbing destinations on the map.
The Class System
The YDS begins with a class describing the type of terrain. Class 1 is walking on a trail; Class 2 is rough cross-country travel; Class 3 is scrambling where you use your hands and a fall could hurt; Class 4 is steep scrambling where many climbers want a rope. Class 5 is technical rock climbing requiring rope, protection, and belaying. Everything climbers usually mean by "the grade" lives inside Class 5, which is why every rock grade begins with "5."
Decoding the 5.x Number
Within Class 5, a decimal expresses difficulty: 5.0 is the easiest technical climbing, rising through 5.9 and on to 5.15. The scale was originally meant to top out at 5.9, but as standards rose it had to keep growing, so it broke past its own ceiling. From 5.10 upward, each number splits into a, b, c, and d to give finer resolution — so 5.10a, 5.10b, 5.10c, 5.10d, then 5.11a, and so on. A 5.11d is therefore just below 5.12a, a small but real step.
Where the Grades Land
A confident beginner climbs in the 5.5–5.8 range; 5.9 and 5.10 mark the transition to intermediate. Breaking into 5.11 is a meaningful milestone for recreational climbers, and 5.12 represents strong, dedicated ability. The 5.13 band belongs to advanced climbers training hard, while 5.14 and 5.15 are the territory of elites and professionals. Tommy Caldwell and Kevin Jorgeson's free ascent of the Dawn Wall on El Capitan featured pitches up to 5.14d, among the hardest big-wall free climbing ever done.
R and X: The Danger Ratings
A distinctive feature of the YDS is its protection rating, borrowed from American film classifications. A route with sparse or poor protection may carry an R, warning of long, dangerous falls; an X means a fall could be fatal. These letters are independent of the difficulty number, so a 5.9 R can be far more serious than a well-protected 5.12. The system thus separates how hard a route is from how dangerous it is — a distinction the pure French number does not make.
Aid and the A and C Grades
The YDS also covers aid climbing, where the climber uses gear to make upward progress. Aid grades run A0 to A5, with A0 meaning occasional pulling on gear and A5 meaning long stretches of bodyweight-only placements where a fall could be enormous. A "clean aid" variant uses C grades for protection placed and removed without a hammer. Big-wall routes often combine a free grade with an aid grade, such as 5.9 A2.
Converting to Other Systems
Rough conversions help travellers. YDS 5.10a sits near French 6a+ and UIAA VI+/VII-; 5.11d aligns with French 7a; 5.13a is around French 7c+. But these are approximations, and the YDS's danger ratings have no equivalent in the French number, so a runout American route can feel far bolder than its grade suggests. Treat conversions as a starting point and let the first routes of a trip recalibrate your sense of the scale.
Explore on the map
The YDS is the key to climbing across the United States, from Yosemite's walls to the desert towers of Utah. Use the interactive map to find American crags and read their routes in the system that grew from the Sierra granite.