Shoes sold by WMS are US size unless the item description states otherwise.

Adult Men's

Small = 8-9

Medium = 10-11

Large = 12-13

X-Large = 14

Adult Mens and Womens Shoe Size Conversion Table (from http://www.i18nguy.com/)
M/W indicates Men's or Women's Sizes. Other systems are for either gender.

System		Sizes																System
Europe		35	35½	36	37	37½	38	38½	39	40	41	42	43	44	45	46½	48½	Europe
Mexico							4.5	5	5.5	6	6.5	7	7.5	9	10	11	12.5	Mexico
Japan	M	21.5	22	22.5	23	23.5	24	24.5	25	25.5	26	26.5	27.5	28.5	29.5	30.5	31.5	Japan	M
	W	21	21.5	22	22.5	23	23.5	24	24.5	25	25.5	26	27	28	29	30	31	Japan	W
U.K.	M	3	3½	4	4½	5	5½	6	6½	7	7½	8	8½	10	11	12	13½	U.K.	M
	W	2½	3	3½	4	4½	5	5½	6	6½	7	7½	8	9½	10½	11½	13	U.K.	W
Australia	M	3	3½	4	4½	5	5½	6	6½	7	7½	8	8½	10	11	12	13½	Australia	M
	W	3½	4	4½	5	5½	6	6½	7	7½	8	8½	9	10½	11½	12½	14	Australia	W
U.S. & Canada	M	3½	4	4½	5	5½	6	6½	7	7½	8	8½	9	10½	11½	12½	14	U.S. & Canada	M
	W	5	5½	6	6½	7	7½	8	8½	9	9½	10	10.5	12	13	14	15.5	U.S. & Canada	W
Korea (mm.)		228	231	235	238	241	245	248	251	254	257	260	267	273	279	286	292	Korea
Inches		9	91/8	9¼	93/8	9½	95/8	9¾	97/8	10	101/8	10¼	10½	10¾	11	11¼	11½	Inches
Centimeters		22.8	23.1	23.5	23.8	24.1	24.5	24.8	25.1	25.4	25.7	26	26.7	27.3	27.9	28.6	29.2	Centimeters
Mondopoint		228	231	235	238	241	245	248	251	254	257	260	267	273	279	286	292	Mondopoint

Boys Shoe Sizes

Europe	29	29.7	30.5	31	31.5	33	33.5	34	34.7	35	35.5	36	37	37.5	Europe
Japan	16.5	17	17.5	18	18.5	19	19.5	20	20.5	21	21.5	22	22.5	23	Japan
U.K.	11	11.5	12	12.5	13	13.5	1	1.5	2	2.5	3	3.5	4	4.5	U.K.
U.S. & Canada	11.5	12	12.5	13	13.5	1	1.5	2	2.5	3	3.5	4	4.5	5	U.S. & Canada