Here is the Xero Shoes sandal size guide.

While we know that choosing a size is very personal, we recommend leaving a space of 0.5 to a MAXIMUM of 1 cm.

Remember that measurements may vary depending on the measuring instrument and technique.

ATTENTION: Xero has "men's" and "women's" sizing. They are not equivalent to each other. Men's sizes are smaller and wider.

Men
Size	Inner length	Inner width
39	24.5	10.3
40	24.8	10.4
41	25.5	10.5
42	26.6	10.7
43	27.5	10.9
44	28.2	11.1
45	29.6	11.3
46	29.8	11.5
47	31	11.7
48	31.5	11.9
Women
Size	Inner length	Inner width
35.5	22.8	9.4
36.5	23.8	9.8
37.5	24.3	9.8
38.5	25	10
39.5	26.1	10.2
40.5	26.9	10.4
41.5	27.5	10.6
42.5	28.5	10.8