Age labels are a starting point. Height is the number that actually fits the child.
Age labels are averages
A label such as 4Y refers to the average four-year-old in the manufacturer's home market, not to your child. Children of the same age can differ by more than fifteen centimetres in height.
European height sizing
EU children's sizing is labelled directly in centimetres of height (98, 104, 110). That makes it the most transferable system: measure the child, pick the nearest number up.
Baby sizing by months
Baby clothing uses month ranges, which similarly track average growth. Newborns often skip the newborn size entirely. Check the height range printed on the label rather than the month figure.
Allowing for growth
Buying one size up is reasonable for outerwear, but oversized daywear can be a trip hazard for new walkers. Measure every three to four months during growth spurts.
Frequently Asked Questions
How often should I re-measure?
Every three to four months for under-fives, twice a year for older children.
Do US and EU kids sizes align?
Loosely. US uses ages and T-sizes while EU uses height in centimetres, so converting via height is safest.