 The waterline belt of the Admiral @-@ class ships was 12 inches ( 305 mm ) thick , angled 12 ° outwards partly to keep the belt inside the bulge structure and allow torpedo hits to vent to the atmosphere . This angle also increased the armor 's relative thickness to horizontal , close @-@ range fire , albeit at the cost of reducing its relative height which increased the chance of plunging shellfire going over or under it . This sloped belt made their armor comparable to the 13 inches ( 330 mm ) found in the latest British dreadnoughts . It ran some 562 feet ( 171 @.@ 3 m ) , from the forward edge of ' A ' barbette to the middle of ' Y ' barbette . Forward of this the belt thinned to six inches before further reducing to 5 inches ( 127 mm ) and ending in a five @-@ inch ( 127 mm ) bulkhead well short of the bow . Aft of the midships section the belt reduced to six inches ( 152 mm ) ; it did not reach the stern , but terminated at a five @-@ inch bulkhead . This belt had a height of 9 feet 6 inches ( 2 @.@ 9 m ) , which 4 feet ( 1 @.@ 2 m ) was below the designed waterline . Above it was the seven @-@ inch middle belt , 7 feet ( 2 @.@ 1 m ) high , and the five @-@ inch upper belt , which was 9 feet ( 2 @.@ 7 m ) high . The middle belt stretched between ' A ' and ' Y ' barbettes , ending in four @-@ inch transverse bulkheads at each end . The upper belt only ran from ' A ' barbette to the end of the machinery spaces and ended in another four @-@ inch transverse bulkhead . Five of Hood 's decks were armoured with thicknesses varying from .75 to 3 inches ( 19 to 76 mm ) , with the greatest thicknesses over the magazines and the steering gear . Immediately adjacent to ' A ' and ' Y ' barbettes the main deck was five inches thick to protect the magazines . 
