I want to adapt a pair of pants to add elastic to the waistband. I have a particular "stretchiness" in mind for this project, but don't know how that relates to a given thickness, width, material, or other characteristic of any particular elastic product.
Is there any standardized terminology for relative stretchiness that I could use when talking to a sales assistant? Are there better ways to choose what elastic to use for a project than standing in the store and pulling on samples to guess how well they would work?
I'm looking for general advice rather than "here's what's best for your pants" -- because this does come up in multiple projects :)