Key takeaways
- The YDS is the US system for rating hiking, scrambling, and climbing difficulty.
- Classes 1–4: Class 1 (walking), 2 (rough hiking), 3 (scrambling), 4 (exposed scrambling, rope sometimes used).
- Class 5 is technical roped climbing, subdivided by decimals from 5.0 to 5.15 (with letter grades a–d at 5.10+).
- Higher decimals mean harder climbing; the system also adds protection (R/X) and commitment grades.
What the YDS is
The Yosemite Decimal System (YDS) is the standard system in the United States for rating the difficulty of hikes, scrambles, and climbs. It sorts terrain into five classes and then finely grades technical climbing with decimals — giving US climbers a shared language to gauge how hard a route is before they start.
The five classes
- Class 1 — walking on a trail.
- Class 2 — rough hiking, occasional hand use.
- Class 3 — scrambling; hands needed, a fall could injure.
- Class 4 — steep, exposed scrambling; a fall could be fatal, rope sometimes used.
- Class 5 — technical roped climbing, graded by decimals.
The 5.x grades
Within Class 5, difficulty runs from 5.0 upward to about 5.15. From 5.10 on, each number splits into letters a–d (5.11a–5.11d) for precision. Grades may also carry protection ratings (R, X) and an overall commitment grade.
A climber reads a guidebook route as ‘5.9’ and knows it’s solidly within their ability, while a neighboring ‘5.12c’ is a project — and they note a Class 3 approach scramble before the technical climbing begins.
Converting grades
The YDS decimal grades map to other systems like the French scale — see YDS vs French and our grade converter. Bouldering uses the separate V-scale.
The bottom line
The Yosemite Decimal System is the US's common language for difficulty, spanning everything from a flat trail (Class 1) to the world's hardest rock climbs (5.15). Knowing the classes (especially the jump from Class 4 scrambling to Class 5 climbing) and how the 5.x decimals and letter grades escalate lets you read a route's difficulty before you commit.
Frequently asked questions
What is the Yosemite Decimal System?
The Yosemite Decimal System (YDS) is the United States' standard system for rating the difficulty of hiking and climbing terrain. It uses five classes — from Class 1 walking up to Class 5 technical climbing — and subdivides Class 5 with decimals (e.g., 5.7, 5.12) to grade rock-climbing difficulty.
What do the YDS classes mean?
Class 1 is walking on a trail; Class 2 is rough hiking, maybe using hands occasionally; Class 3 is scrambling where you use your hands and a fall could injure; Class 4 is steeper, exposed scrambling where a fall could be fatal and a rope is sometimes used; and Class 5 is technical roped climbing, graded further by decimals.
How do the 5.x decimal grades work?
Within Class 5, difficulty runs from 5.0 (easy) upward, currently to about 5.15. From 5.10 onward, each number is split with letters a–d (e.g., 5.11a to 5.11d) for finer distinction. Higher numbers mean harder climbing. Grades can also carry protection ratings (R, X) and an overall commitment grade (I–VII).
Sources
- Grading systems — American Alpine Club
- Route grades — The Mountaineers