Halsa runs pretty true to size and a little on the wide side.
M(medium)=B  W(wide)=C.

 
Inches CM US Women's Euro #1 All Euro #2 All Mexico All    Japan Women's UK Women's Australian Women's Korea / Mondopoint
8 1/3" 21.2 4 34 34 21 20 2½ 2½ 212
8 1/2" 21.6 4½ 34.5 34-35 21.5 20.5 3 3 216
8 2/3" 22 5 35 35 22 21 3½ 3½ 220
8 5/6" 22.4 5½ 35.5 35-36 22.5 21.5 4 4 224
9" 22.9 6 36 36 23 22 4½ 4½ 229
9 1/6" 23.3 6½ 36.5 36-37 23.5 22.5 5 5 233
9 1/3" 23.7 7 37.5 37-38 23.5-24 23 4½ 5½ 237
9 1/2" 24.1 7½ 38 38 24 23.5 5 6 241
9 2/3" 24.6 8 38.5 38-39 24.5 24 5½ 6½ 246
9 5/6" 25 8½ 39.5 39-40 25 24.5 6 7 250
10" 25.4 9 40 40 25.5 25 6½ 7½ 254
10 1/6" 25.8 9½ 40.5 40-41 26 25.5 7 8 258
10 1/3" 26.2 10 41.5 41-42 26 26 7½ 8½ 262
10 1/2" 26.7 10½ 42 42 26.5-27 26.5 8 9 267
10 2/3" 27.1 11 42.5 42-43 27 27 8½ 9½ 271
10 5/6" 27.5 11½ 43.5 43-44 27.5 27.5 9 10 275
11" 28 12 44 44 28 28 9½ 10½ 280
11 1/6" 28.4 12½ 44.5 44-45 28.5 28.5 10 11 284
11 1/3" 28.8 13 45.5 45-16 29 29 10½ 11½ 288
11 1/2" 29.2   46 46 29-29.5       292
11 2/3" 29.6   46.5 46-47 29.5       296
11 5/6" 30.1   47.5 47-48 30       301
12" 30.5   48 48 30.5       305
12 1/6" 30.9   48.5 48-49 31       309
12 1/3" 31.3   49.5 49-50 31.5       313
12 1/2" 31.8   50 50 32       318
12 2/3" 32.2       32-32.5       322
12 5/6" 32.6       32.5       326