Hydrogen | News blog

Size guide

Measure the foot and match insole length (IN / CM). We sell mainly to the US — sizes below show USA first, plus UK, EU, IN, CM, and approximate age. Ages are a guide only — measuring is more accurate.

Tip: Kids’ feet grow fast. If you’re between sizes, choose the larger one so the shoe isn’t too small.

Size chart

USA	UK	EU	IN	CM	Age
4	3	19	4.5	11.5	6-12 Month
5	4	20	4.7	12	9-15 Month
5.5	4.5	21	4.9	12.5	12-18 Month
6	5	22	5.1	13	15-24 Month
6.5	5.5	23	5.3	13.5	18-24 Month
7	6	23.5	5.5	14	2-2.5 Year
8	7	24	5.7	14.5	2-3 Year
8.5	7.5	25	5.9	15	2.5-3.5 Year

IN / CM is insole length. Age is approximate. UK / EU are approximate conversions.

How to measure

Have your child stand with the heel against a wall.
Mark the tip of the longest toe.
Measure heel-to-mark in centimetres.
Match that length to the IN or CM column (or size up if between sizes).