If you need to wear a tuxedo vest, measuring is something that does not have to be spot-on. It will be adjustable at the neck and waist area. Most vests are offered on a small, medium, large, and extra large range. The chest and overarm measurement that's taken for your jacket might effect the girth or size of the vest, but this shouldn't be much of a problem since its adjustable. Whether or not its a full-back may also effect the fit. Children's sizes are measured on the same basis and can be ordered in the same colors and styles as the men's vests.