Larger Than Waist Size
A dress belt should be one or two sizes larger than the size of your waist. The reason for this is the size of your pants typically corresponds to the size of your waist. The belt is placed over your pants, therefore, the extra inch or so may be necessary.
The Same As The Waist Size
Many times, you will find that purchasing the same belt size as your waist size will fit appropriately. Belts have many holes. Therefore, you can adjust the belt to your needs. Not wearing a belt that is two inches more than your waste will not make that much of a difference.
A dress belt should be about the same size as your waist. If you are unsure of what size belt to purchase, then you should buy one that is at most two inches larger than your waist. It is always easier to add holes to a belt than it is to lengthen a belt.