Children's clothing sizes are typically based on age or height, but the labelling varies between UK, EU, and US brands. Our children's clothing size guide provides conversion charts from newborn through to age 14 to 15, covering both boys and girls. A UK age 3 to 4 is equivalent to EU size 98 to 104 (height in cm) and US size 3T to 4T. Age 7 to 8 is EU 122 to 128 and US 7 to 8. Because children grow at different rates, we recommend checking the height measurement alongside the age guide for the most accurate fit.