heres what i do. I measued 15 gallons into my trash can that i use for water then marked the outside with a piece of duct tape. i got a submersible pump from the local fish store and a lenght of clear vinyl hose also from the fish store and attached it to the pump. I took a piece of pvc pipe (mines about 4 foot, it depends on your room) and shoved the vinyl hose into the pipe so that i can easily reach the plants in the back corner of my room (really bad back) Now just measure the nutes for 15 gallons, plug the pump in and pump into a gallon jug while you count mississippis or whatever. Mine works out to 15 mississippi for 1 gallon. just dont water high cuz youll fuck the count up FOR sure lol.