Elevation - 1000' = ??? (Read 401 times)

Has anyone seen a standard elevation to miles computation for elevation on a run? For instance, I can run 8 miles with no elevation gain in about 65 minutes pretty easily. But - through in a nice 1200' (with a net of 0) and I'm at 75 minutes. Make that 2000' on trails and it's a little over 90 minutes. I'm wondering this for a couple of reasons. 1. Wondering what my equivalent mileage is. and 2. Say I'm doing a 20 mile trail run with 4000' of elevation, when should I tell my wife to pick me up? :-) and as a bonus, it'd be cool for helping to figure out calorie burn. Cheers!