To better describe the climbing difficulty level, a number of classification system were invented. However today the most prevalent system is the Yosemite Decimal System (YDS).

The YDS splits the difficulty level into two (2) sections :

• The Grade
• The Class

The Grade

The Grade is identified by a roman numeral and indicates the length and the quality of the climbing route. Here's the explanation from Wikipedia:

• 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 Class

The Class is identified on a scale of 1 to 5 and identifies the hardest section of the route.

• Class 1 is walking with a low chance of injury and a fall unlikely to be fatal.
• Classes 2 and 3 are steeper scrambling with increased exposure and a greater chance of severe injury, but falls are not always fatal.
• Class 4 can involve short steep sections where the use of a rope is recommended, and un-roped falls could be fatal.
• Class 5 is considered true rock climbing, predominantly on vertical or near vertical rock, and requires skill and a rope to proceed safely. Un-roped falls would result in severe injury or death.

This class numbering scheme can also be sub-divided into point values like 5.7, or 5.15 indicating further difficulty. The hardest route to date is a 5.15a.