It has been a while since I had to calculate fuel for a white gas stove but my memory has it that you need 2oz per person per day. If all you are doing is boiling water, you may actually get by with less. Test it at home. Weigh your fuel bottle; boil 3 cups of water, and weigh your fuel again.
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If I wouldn't eat it at home, why would I want to eat it on the trail?