Measure the child and use the measurements, not the age. Age labels on children’s patterns describe an average that few actual children match, and the same child can be two sizes apart on different pattern brands.
Take three measurements. Height, chest and waist. For trousers, add the hip and the inside leg. Measure over close-fitting clothes with the child standing normally, which is harder than it sounds.
Height is the most useful single number for children’s patterns, because most are drafted around it. Chest decides the size for tops; height then tells you how much to lengthen or shorten.
Blend between sizes without hesitation. Children are very often one size in the chest and another in height. Trace the chest size for the bodice, then adjust the length at the lengthen and shorten lines to match the height. This is normal, not a compromise.
Check the finished garment measurements, not just the body measurements. They tell you how much ease the design has, which matters more on children’s clothes, where movement is the point.
Do not size up for growth by default. A garment two sizes too big does not fit and is not worn, so the growth is wasted. Add length at the hem and cuffs instead, where it can be let down.
Re-measure often. Children change size faster than you will remember, and a measurement from six months ago is fiction.
Questions people actually ask
My child is between two sizes.
Take the larger for chest and hip, then shorten to the right height. It is easier to reduce length than to add width later.
Do nappies affect the fit?
Yes, considerably, on trousers and anything fitted at the hip. Many patterns for the youngest sizes account for it, but check the finished measurements rather than assuming.
Last reviewed 2026-08-11