Yosemite Decimal System

The Yosemite Decimal System (YDS) is a three-part system used for rating the difficulty of walks, hikes, and climbs, primarily used by mountaineers in the United States and Canada. It was first devised by members of the Sierra Club in Southern California in the 1950s as a refinement of earlier systems, particularly those developed in Yosemite Valley, and quickly spread throughout North America.

The class 5 portion of the class scale is primarily a rock climbing classification system, while classes 1–2 are used mainly in hiking and trail running. Class 3 describes easy and moderate climbing (i.e. scrambling), with varying amounts of exposure. Class 4 is an "in-between" rating that describes a very exposed scramble, corresponding roughly to the IFAS classification of PD+. Climbers, specifically those involved with technical class 5 climbing, often abbreviate "class 3" and "class 4" to "3rd" and "4th" respectively.

Originally the system was a single-part classification system. "Grade" and "protection" categories were later added to the system. The new categories do not apply to every climb and usage varies widely. "Grade" describes the amount of time needed to complete a climb, and "protection" describes the availability and quality of places on a climbing route where a climber may utilize climbing protection.

Class 5 is subdivided into parts, currently 5.0 to 5.15. Ratings above 5.9 are further subdivided, for example, 5.10b or 5.15c. When writing out a full YDS rating, grade is added after classification, and is followed by protection, so a typical YDS route description would be something like "5.10b VI R". Often the grade is omitted, and just the classification and protection ratings used. If the amount of protection available on a route is not concerning, then the protection rating is omitted as well.

While primarily considered a free climbing system, an aid-climbing designation is sometimes appended, numbered A0 to A5. For example, The North America Wall on El Capitan would be classed "5.8 VI A5" using this mixed system.

Classes

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.

The system was later refined into its modern, well-known form by climbers at Tahquitz Peak in Southern California. The 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 in the region, 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.

The system now divides all hikes and climbs into five classes: The exact definition of the classes is somewhat controversial, and updated versions of these classifications have been proposed.

Class 1

Walking with a low chance of injury, hiking boots a good idea.

Class 2

Simple scrambling, with the possibility of occasional use of the hands. Little potential danger is encountered. Hiking Boots highly recommended.

Class 3

Scrambling with increased exposure. Handholds are necessary. A rope should be available for learning climbers, or if you just choose to use one that day, but is usually not required. Falls could easily be 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

Is considered technical roped free (without hanging on the rope, pulling on, or stepping on anchors) climbing; belaying, and other protection hardware is used for safety. Un-roped falls can result in severe injury or death. Class 5 has a range of sub-classes, ranging from 5.0 to 5.15d,, to define progressively more difficult free moves.

Guidebooks sometimes 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. Information about the difficulty of a summit block is sometimes added. For example, a rating of 3s4 means that most of the climb is class 3 but the summit block is class 4.

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 2018, only one climb is considered to have a difficulty of 5.15d: Silence, first climbed by Adam Ondra in September, 2017.

Classification of climbs between indoor gym, sport and traditional climbing can also vary quite a bit depending on location and history.

A formula that combines average speed, class of climb, distance and elevation gain for use in planning has yet to be published.

Grades

The YDS grade system involves an optional Roman numeral grade that indicates the length and seriousness of the route. The grades are:

Grade	Duration
I	One to two hours of climbing
II	Less than half a day
III	Half a day climb
IV	Full day climb
V	A climb lasting 2–3 days
VI	A climb lasting 4–6 days
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.

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:

Code	Description
G	Good, solid protection
PG	Pretty good, few sections of poor or non-existent placements
PG13	Fair protection, falls may be long but are less likely to 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

• Aid climbing
• Ice climbing
• Grade (climbing)