The overall difficulty of a route is indicated by a Roman numeral. The Arabic number that follows the Roman numeral applies to the hardest move or crux sequence. Thus, with regard to ice routes, a V, 4 may be classed as a serious ice route, whereas a V, 5 will normally be a classic ice route with adequate protection. Alternatively, a mixed route graded V, 6 would be a classic mixed route, whereas a V, 7 would indicate a technically difficult, but well protected mixed route.
Grade I – Uncomplicated, average-angled snow climbs normally having no defined pitches. However, they may have cornice difficulties or long run-outs.
Grade II – Gullies that contain either individual or minor pitches, or steep-angled snow with difficult cornice exits. The easiest buttresses or ridges under winter conditions.
Grade III – Gullies that contain ice in quantity, where there will normally be at least one substantial pitch and possibly several lesser ones. Sustained buttresses and mixed climbs, but only technical in short sections.
Grade IV – Steeper and more technical with vertical sections found on ice climbs. Mixed routes will require a good repertoire of techniques.
Grade V – Climbs which are difficult, sustained and serious. If on ice, long sustained ice pitches are to be expected, whilst mixed routes will require a degree of rock climbing ability and the use of axe torquing and hooking, as well as other winter techniques.
Grade VI – Thin and tenuous ice routes or those with long, vertical sections. Mixed routes will include all that has been defined previously, but more of it.
Grade VII – Mixed routes will be very sustained or technically extreme. Also sustained routes on thin or vertical ice.
Grade VIII – Very hard and sustained mixed routes.