Avia Women's Size Chart:

U.S.A. 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10
U.K. 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

Avia Men's Size Chart:

U.S.A. 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13
U.K. 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5