Yosemite Decimal System
The Yosemite Decimal System (YDS) is a three-part system used for rating the difficulty of walks, hikes, and climbs. It is primarily used by mountaineers in the United States and Canada. The Class 5 portion of the Class scale is primarily a rock climbing classification system. Originally the system was a single-part classification system. In recent years, Grade and Protection categories were added to the system. The new categories do not apply to every climb and usage varies widely. The grades are subjective, reflecting the first ascenscionist 's opinion of the climb's difficulty.
While primarily considered a free climbing system, an aid climbing designation is sometimes appended. For example, The North America Wall on El Capitan would be classed "VI, 5.8, A5" using this mixed system.
YDS class 
The system was initially developed as the Sierra Club grading system in the 1930s to classify hikes and climbs in the Sierra Nevada. Previously, these were described relative to others. For example Z is harder than X but easier than Y. This primitive system was difficult to learn for those who did not yet have experience of X or Y. The club adapted a numerical system of classification that was easy to learn and which seemed practical in its application.
Guidebooks often append some number of stars to the YDS rating, to indicate a climb's overall "quality" (how "fun" or "worthwhile" the climb is). This "star ranking" is unrelated to the YDS system, and varies from guidebook to guidebook.
- Class 1: Walking with a low chance of injury.
- Class 2: Simple scrambling, with the possibility of occasional use of the hands. Little potential danger is encountered.
- Class 3: Scrambling with increased exposure. A rope can be carried but is usually not required. Falls are not always fatal.
- Class 4: Simple climbing, with exposure. A rope is often used. Natural protection can be easily found. Falls may well be fatal.
- Class 5: Technical free climbing involving rope, belaying, and other protection hardware for safety. Un-roped falls can result in severe injury or death.
The original intention was that the classes would be subdivided decimally, so that a class 4.5 route would be a climb halfway between 4 and 5. Class 5 was subdivided in the 1950s. Initially it was based on ten climbs of Tahquitz Rock in Idyllwild, California, and ranged from the "Trough" at 5.0, a relatively modest technical climb, to the "Open Book" at 5.9, considered at the time the most difficult unaided climb humanly possible. This system was developed by members of the Rock Climbing Section of the Angeles Chapter of the Sierra Club.
Increased standards and improved equipment meant that class 5.9 climbs in the 1960s became only of moderate difficulty for some. Rather than reclassify all climbs each time standards improved, additional classes were added. It soon became apparent that an open-ended system was needed and further classes of 5.11, 5.12, etc. were added. It was later determined that the 5.11 climb was much harder than 5.10, leaving many climbs of varying difficulty bunched up at 5.10. To solve this, the scale has been further subdivided above the 5.9 mark with suffixes from "a" to "d". As of 2005[update], several climbs are considered to have a difficulty of 5.15a. Akira, climbed by Fred Rouhling, is claimed to be a 9b (French grade) which translates to YDS 5.15b. Chilam Balam climbed by Bernabé Fernández was rated as 9b+ or 5.15c YDS. Both were controversial, with 'Chilam Balam' downgraded to 9b (5.15b) by Adam Ondra in April 2011.
The original Sierra Club grading system also had a Class 6, for artificial, or aid climbing. This sort of climbing uses ropes and other equipment where progress is made by climbing directly on equipment placed in or on the rock and not the rock itself. Class 6 is no longer widely used. Today aid climbing uses a separate scale from A0 through A5.
Classification of climbs between indoor gym, sport and traditional climbing can also vary quite a bit depending on location and history.
YDS grade 
The YDS grade system involves an optional Roman numeral grade that indicates the length and seriousness of the route. The grades are:
- Grade I: One to two hours of climbing.
- Grade II: Less than half a day.
- Grade III: Half a day climb.
- Grade IV: Full day climb.
- Grade V: Two day climb.
- Grade VI: Multi-day climb.
- Grade VII: A climb lasting a week or longer.
The Grade is more relevant to mountaineering and big wall climbing, and often not stated when talking about short rock climbs.
YDS protection rating 
An optional protection rating indicates the spacing and quality of the protection available for a well-equipped and skilled leader. The letter codes chosen were, at the time, identical to the American system for rating the content of movies:
- G: Good, solid protection.
- PG: Pretty good, few sections of poor or non-existent placements.
- PG13: OK protection, falls may be long but will probably not cause serious injury.
- R: Runout, some protection placements may be very far apart (possibility of broken bones, even when properly protected).
- X: No protection, extremely dangerous (possibility of death even when properly protected).
The G and PG ratings are often left out as they are typical of normal, everyday climbing. R and X climbs are usually noted as a caution to the unwary leader. Application of protection ratings varies widely from area to area and from guidebook to guidebook.
Other systems 
There are other systems used throughout the world. They are covered in the article about Grade (climbing).
See also 
- Reid, Don; Chris Falkenstein (1992). Rock Climbs of Tuolomne Meadows (3rd ed.). Evergreen, Colorado, USA: Chockstone Press. p. 129. ISBN 0-934641-47-1.
- Roper, Steve (1976). The Climber's Guide to the High Sierra. Sierra Club Books. pp. 19–21. ISBN 0-87156-147-6.
- "The Yosemite Decimal System". Climber.org. Retrieved 2009-01-15.
- Mountaineering: The Freedom of the Hills (6th ed.). Seattle: The Mountaineers. ISBN 0-89886-426-7.
- "Adam Ondra Climbs Chilam Balam". UK Climbing. Retrieved 2011-07-28.
- Bjornstad, Eric (1996). Desert Rock – Rock Climbs in The National Parks. Evergreen, Colorado: Chockstone Press. p. 7. ISBN 0-934641-92-7.