Deposits

I'm curious what you all charge for deposits and how you determine it. I'm considering raising mine from 20% to 50%. I'm an editor, so hourly charges are really best for my work. I provide clients with an estimate range based on a minimum and maximum amount of time I think the project will take (I charge hourly), and the deposit is based on the minimum time.

How do you all handle deposits? Are they based on a flat rate or an estimate? What industry are you in?

Thanks!