The simplest way to determine a S&B belt size is to add 2 inches to a men's pant waist size. If the recipient is an odd pant size (33, 35 etc.), add 3 inches to the pant size to obtain the correct belt size. If they wear multiple pant sizes, use the largest size to calculate the correct belt size. This formula works best for chino style pants.
If the recipient typically wears designer denim or low rise pants, you may need to add 3-4 inches to the men's pant waist size.