Is there a teacher's guideline or standard that is applied for the number of hours given to prepare a presentation? I.e. I have heard 3 hours of prep for every 1 hour of presentation is a basic standard, but I don't know where that ratio came from. I work in an agency of billable hours percentage I must maintain, and I'm asked to provide presentations but not given a formula for the number of hours I can have to prepare. It would be helpful to have a standard guideline that I could provide to my employer that would be fair to both them and myself.

Thank you in advance for your answers