[header] How to calculate bmi for children [title] Remove shoes or bulky clothing. [step] While a light t-shirt or shorts are fine, heavy sweaters or jeans and shoes will prevent you from accurately measuring the child's height and weight. Any hair accessories that gather the child's hair on the top of their head also interfere with the height measurement. 
[substeps] Bulky clothing can interfere with an accurate height measurement as well as weight. For example, if the child is wearing a hoodie they won't be able to stand straight against a wall.