Probably a comical reference to 'the grade calculator', where you put in the grade of the constituent parts and get out the grade of the whole thing. It's not actually a real thing (the real world being nuanced as it is.)
Press Release The Nest - New climbing wall in Hayes, West London
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News Pete Whittaker flashes Ronny Medelsvensson (Trad 8b)
Pete Whittaker has flashed Ronny Medelsvensson (8b) on the Profile Wall in Jøssingfjord, Norway. Pete is in fine form at the moment having climbed his long-term project 'Recovery Drink' (8c+) on the same wall last week. Ronny Medelsvensson...