American	UK	European	Japanese
6	5.5	39	24
6.5	6	39.5	24.5
7	6.5	40	25
7.5	7	41	25.5
8	7.5	41.5	26
8.5	8	42	26.5
9	8.5	43	27
9.5	9	43.5	27.5
10	9.5	44	28
10.5	10	44.5	28.5
11	10.5	45	29
11.5	11	45.5	29.5
12	11.5	46	30
12.5	12	47
13	12.5	48

Widths

AA	A	B	C	D	E	EE	EEE
Very Narrow		Narrow		Medium	Wide	Extra Wide

The most common width is medium - D