For toddlers and small kids, use the first size chart which is for both girls and boys. For older children, use the respective chart for girls and boys. Please note that these charts only is a guide to your child’s clothing size, and that the sizes may vary between different brands.
Children’s clothes – International size chart The American, British and Australian sizes are based on the age of the child, while in Europe the size is based on the child’s height in centimeters. Some US sizes include a “T”, which stands for toddler.
However, the best way is to take accurate measurements of your kid’s body using a cloth measuring tape. You may then refer to a size chart to know the corresponding clothing size to your child’s measurements. American sizes, along with British and Australian clothing sizes, are traditionally based on age.