– Let your child wear normal socks and no shoes
– Place both feet on a blanco piece of paper against the wall
– Paper and heels should be placed securely against the wall
– Make the child stand up straight, knees bent a little
– Mark the longest part of the feet (either the first, or second toe)
– Measure the distance as shown
– Use the size converter to choose the correct size, choose the shoe size that fits the bigger foot.

Or you can use Pitter-Pad; an iPad App that measures children shoe sizes. It features an easy to use step-by-step interface that accurately measures each foot’s length and width.

Please keep in mind:
– Most children feet grow two sizes a year
– Allow new shoes to be 12-16 mm bigger than the longest toe
– Shoes that are only 5mm longer should be regarded as too short and be replaced

Tips for healty, happy feet:
– Remember to check your child`s shoe size often, at least twice a year.
– Wash children’s feet daily & dry them carefully. Also between those little toes!
– Regularly trim the toenails, but never cut down the side of the nails or cut them too short.
– Give you’re child’s feet a regular check-up: check toenails and check for any signs of redness, irritated skin and/ or rubbing.
– Don’t forget to check their socks: a good sock should fit & breathe just like a good shoe. Cotton or wool are good materials. Go for at least 60% cotton.
– When possible: go barefoot!

source:

size converter: Wikipedia.org / Claus Färber