For adult sweatshirts we use US Regular, and for T-Shirts we use US Tight fits. So it is advised to order at least one size larger than your standard size for adult T-Shirts
Also,don’t forget, every child is very different so, you have to measure your children and check the body measurements table what size is regardless of age.
Please make sure you checked the size chart correctly before placing your order.Products are made-to-order, so they can not return or exchance.
You can find the Size Guide in product description over Credit Card banners.