painting fastback

Hi, Going to paint my 67 fastback and trying to figure out how much paint I need , I bought a gallon of primer from tcp global and want to buy single stage urethane paint , I need to spray the engine bay, hood underside trunk compartment and lid underside plus door jambs and door edge and bottom, first car I ever painted so am probably going to use more than a pro from what I have read , was told a gallon but I was thinking I need 2 , anyone have any knowledge on the amount I need, Thanks
If you never sprayed before dont use a single stage. Its so much harder to spray. I always figure a gallon of color for the outside & a quart for the jambs. Depending on what color sealer or primer you are spraying over spray at least 3 coats. Are set on spraying it yourself ?