Per person:

We plan on a gallon a day for drinking and cooking. 2 gallons per male shower, 3 gallons per female shower (more hair rinsing needed). 1-3 gallons each time we wash dishes (depends on how difficult to clean and whether we use sea water for the pre-wash). We don't use sea water in LIS for washing, but do where it's cleaner. (+2 gallons if we visit a beach to rinse the dog on the stern.) We generally wash clothes ashore in marinas.

So it comes out to about 5 gallons per day per person, more or less.