Size chart above is for the jacket itself, NOT your childs measurement. Measure your childs chest and waist while they are wearing the type of clothing they would normally wear under their jacket. If they are going to wear large bulky sweaters and such, measure them while they are wearing these bulky items or their jacket will be too tight. Add about 2"-3" for breathing room then choose the correct size jacket from the chart above. Size chart is approximate but close. For example if your childs chest measurement is 25", then adding 2-3 inches to that which would be 27"-28", choose a size XL as it's better for it to be a little larger than too small.Please keep in mind, we NEVER have to do size exchanges for smaller sizes, it is always to exchange for a larger size. Remember too that your children are growing, so it's better for it to be too big than too small.