[header] How to determine belt size [title] Wear pants that fit well. [step] Put on a pair of jeans or pants that you will wear frequently with a belt. These pants should not be too loose or too tight so that you will be able to get an accurate measurement of your waist. 
[substeps] The most important thing is to choose a pair of pants that fit how your pants usually fit. You want to get a belt that will fit with the pants you normally wear.