Size
foot length
0-3M
 1
3 ⅝
9
3-6M
 2
3 ¹⁵/₁₆
10
6-12M
3
4 ⁵/₁₆
11
12-18M
4
4 ⅝
11 ¾
18-24M
5
5
12 ½ 
Size
foot length
XS
3
4
5
6
4 ⁵/₁₆
11
4 ⅝
12
4 ¹⁵/₁₆
12 ½
5 ⁵/₁₆
13
S
7
8
5 ⅝
14
5 ¹⁵/₁₆
15
M
9
10
6 ¼
16
6 ⁹/₁₆
17
L
11
12
6 ¹⁵/₁₆
17 ½
7 ¼
18 ½
Size
foot length
0-3M
3 ⅝
7-10
3-6M
3 ¹⁵/₁₆
8-11
6-12M
4 ⁵/₁₆
9-12
12-18M
4 ⅝
10-13
18-24M
5
11-14
Size
foot length
0-3M
3-4
9-12
6-12M
5
11-14
12-24M
6-7
12-15
2T-3T
8-9
14-17
4T-5T
10-11
15-18

Measuring Tips

Put a piece of paper on the ground. Stand barefoot on the paper. Draw outline of foot with a pen. Use measuring tape to measure length of foot on the paper.