Europe	Mondopoint (Comfort Fit)	Foot Length (cm)	Men / Unisex (US)	Women (US)	UK
25	15	-	8 (Kids')	-	7
25	15.5	-	8 (Kids')	-	7
26	16	-	9 (Kids')	-	8
26	16.5	-	9 (Kids')	-	8
27	17	-	10 (Kids')	-	9
28	17.5	-	11 (Kids')	-	10
29	18.5	-	12 (Kids')	-	11
30.5	19.5	-	13 (Kids')	-	12
31	20	-	13.5 (Kids')	-	13
32	20.5	-	1	-	13.5
33	21	-	2	-	1
34	21.5	-	3	-	2
35	22	21	4	5	3
36	22.5	21.5	4.5	5.5	3.5
36.5	23	22	5	6	4
37	23.5	22.5	5.5	6.5	4.5
38	24	23	6	7	5
38.5	24.5	23.5	6.5	7.5	5.5
39	25	24	7	8	6
40	25.5	24.5	7.5	8.5	6.5
40.5	26	25	8	9	7
41	26.5	25.5	8.5	9.5	7.5
42	27	26	9	10	8
42.5	27.5	26.5	9.5	10.5	8.5
43	28	27	10	11	9
44	28.5	27.5	10.5	11.5	9.5
44.5	29	28	11	12	10
45	29.5	28.5	11.5	-	10.5
45.5	30	29	12	-	11
46	30.5	29.5	12.5	-	11.5
47	31	30	13	-	12
47.5	31.5	30.5	13.5	-	12.5
48	32	31	14	-	13
48.5	32.5	31.5	14.5	-	13.5
49	33	32	15	-	14
50	33.5	32.5	15.5	-	14.5
51	34	33	16	-	15

Cross country ski boots mostly come in Euro sizes, making it difficult for non-Europeans to dial in the right fit. Visiting a bootfitter is the best way to ensure a proper fit, and a proper fit is paramount in cross country skiing. It's always better to size down than size up — a boot with too much room can cause blisters.