to figure out the ratio?

i am thinking of buying a gallon of local honey or even two if the price is right. if i was to use one gallon of honey how do you figure out how much water to use?
i was thinking as well of when i rack off into the second that i would take a couple of one gallon jugs and put frozen fruit into them and fill with mead to flavour them. sound like a good idea or not?
need to figure out how to figure the ratio

A gallon of honey is ~ 12 lbs. I use 1 gal of honey plus 5 gals cider for my cyser, so my gravity is usually in the low 100's to 110's with the extra sugar from the cider. If you did a 5 gal total volume batch with just water diluting the honey, you'd probably have OG's in the 1.090's, which would put you solidly in the lower ranges of a standard mead. Add some fruit puree or juice in secondary, and you've got a great melomel....