|７級 [7-kyuu]||4a|| a|
|六段[Wheel of life]|
The Japanese system for grading boulder problems originated in Ogawayama. It's based on the same principle as the kyū/dan system first applied to martial arts by Kano Jigoro, the founder of judo; so if you have flailed about with arms, legs, or sticks, all dressed up in a pyjamas you know how it goes: 10-kyū or jūkyū, the tenth grade, demands the least amount of skill. As your skill progresses you pass 9-kyū, 8-kyū, and down to 1-kyū. After that you reach shodan, the first dan, or literally the “first step”. This is where you get a black belt – and serious training is supposed to commence. In bouldering shodan starts around the 7a+/V7 mark, and it may be possible to reach the dizzying heights of the sixth step, rokudan, by climbing “Wheel of Life”, 8c+ on the Fontainebleau scale.
Or so I've been told.
Included is my best guess on a conversion table, based on personal experience and input from my betters. Unfortunately, I've never been to Hueco, so for a comparision with the Hueco-scale you have to find information elsewhere.
Apart from the kyū/dan system there is an other system in place in Japan for grading boulder-problems: the Toyota a-b-c grades. I hesitate to call it a major grading system since it only seems to be in use in the Toyota area. Toyota is a massive bouldering area though, with a history that predates a lot of the bouldering areas worldwide, so it would be silly not to include it in my table.
Diamond slab, Toyota grade d.