In the sport of bouldering, problems are assigned technical grades according to several established systems, which are distinct from those used in regular climbing. Bouldering grade systems include the "B" system, Hueco "V" grades (also known as the V-scale), Fontainebleau technical grades, route colours, and overall difficulty grades, Peak District grades, and British technical grades.

The old "B" grade system, introduced by John Gill, has only three categories, B1, B2 and B3. B3 problems are those that have only been completed once. B2 as problems that are "harder than B1". B1 problems are those relating to "a hard toprope climb".

In Europe the Fontainebleau grading is the most widely used. This system ranges from 1a to 8c (the equivalent of V15 or B15), it is rare to find problems easier than 2b. The system was first devised to classify the sandstone climbing in the Fountainebleau forests in France, but is now widely used also in other bouldering areas around the world.

In North America, the "V" grades devised by John 'Vermin' Sherman at Hueco Tanks are prevalent, having largely displaced the older "B" grades. The "V" system currently covers a range from V0 to V16. At the easier end of the scale, some use the designation VB (for V-basic) for problems slightly easier than a V0. Particularly at the lower end of the scale, the grades can also be postfixed with "+" (harder) or "-" (easier) to further distinguish the difficulty range within a single grade.

It is difficult to directly compare bouldering grades to climbing grades. A B1 problem was defined by John Gill in 1969 as a 5.10, but in 1987 as a 5.12. This highlights the constant evolution of the "B" scale.

The 'V' system corresponds to the Yosemite Decimal System better, more so for people who are similarly proficient at both short, powerful climbs and long, endurance dependent ones. The following is a rough translation (but not an exact equivalence):

• V0- <---> 5.9
• V0 <---> 5.10-
• V0+ <---> 5.10
• V1 <---> 5.10+
• V2 <---> 5.11-
• V3 <---> 5.11+
• V4-V6 <---> 5.12
• V7-V9 <---> 5.13
• V10-V13 <---> 5.14
• V14+ <---> 5.15+

A V3 boulder problem is similar to a 5.11+ climb; the difficulty level of the hardest move found on any 5.11+ climb would be comparable to those on a short V3 boulder problem. However most 5.11+s wouldn't have individual moves as hard as that of a V3, rather the combined endurance challenge of many easier moves on a 5.11+ put together is about the same as the few hard moves of a V3.

People sometimes use bouldering grades to describe the crux of a long roped climb to give a sense of how much pure strength is required to do the climb. i.e A 5.12b climb that contains a V4 crux at the start and very easy terrain thereafter is suited to a climber with lots of power and little endurance, while another 5.12b that contains many sections of V1 but with no rest in between is more suited to a climber with a lot of endurance and little maximum finger strength.

Also on climbing scales is the United Kingdom standard scale (or UKS) this consists of letters and numbers detailing the general difficulty level of the whole climb. It works by using a number between four and seven, this 'initial grade' is the general level of difficulty the climber may experience. A secondary grade is added on to this as a measure of difficulty with that numerical level, for example; 5c, meaning level five, grade c. Separating each level are grades a, b and c; a being the lowest and c being the highest. As a way of a 'for instance', 4c is higher than 4a, while 5a is higher than 4c, this neatly splits the grading system 12 separate grades ranging from 4a to 7c. It is also accepted by many professional climbers to grade routes by levels outside of this scale, this is professionally indicated as 7c+. See below for a full conversion table.

See also

• Grade (climbing)

Climbing