Figuring Panel Lengths

I am wandering if there is a formula that you can use to determine your panel lengths on valleys or hips. So to clarify, I do not currently have a panel machine and have another contractor form our panels onsite. They want a cut sheet telling them what lengths to cut all of our panels. I understand what I need to in order to quote standing seam projects accurately and order the proper amount of materials/coil. What I am looking for is suggestions or formulas that will work to calculate how many panels at what lengths for tough areas like hips and valleys. What is the best way that you have found to do this with as little waste as possible? Thanks.