You might have tried pants in many stores and most likely your waistline size varies by quite a lot. Here is a chart of an ordinary “36 inch waistline pant across many big name retail stores. Old Navy “36 inch is really a “41 inch waist size. Sure it is great for Thanksgiving and the ego but you are the only one who really knows your true size.
“I said, ‘I do not fear those pants / With nobody inside them.’
I said, and said, and said those words. / I said them. But I lied them.”
—Dr. Seuss
via-Esquire