Mix the one gallon as specified in the instructions. Then decant into one quart bottles topped off and lids applied tightly. I keep mine in 250ml bottles for one shot use. I can get two 35mm or one 120 film per 250ml bottle using 1+1. You can get more than one film per mix by adding 10% to time per each successive roll. As an experiment, I ran four seperate rolls of 24 exposure 35mm film with no noticable degradation, from the same developer mix. I don't recommend this for practical reasons though.