I really enjoy shopping for groceries. This week, I went to Walmart, and spent about $50 on groceries for the week. When I got home, I was curious about what I had gotten. I was hoping I actually had a whole week's worth of food; it seemed to me as though I had far more than a week's worth.
Here is what I bought (click for a giant version):
So, I was curious how this compared to my calorie intake. Assuming I might eat about 2000 calories per day (and ideally I would eat a bit less and lose weight, but in fact I think I eat a bit more, so I just chose this as a nice round number), I need 14,000 calories per week.
The groceries above come out to 12,475 calories - not quite a week's worth.
Of course, some of the groceries above will likely be wasted, some (like the jelly) will last beyond the week, and some rely on ingredients not shown but that I already own (like peanut butter to go with the bread and jelly, and pasta for the spaghetti sauce). And I also have other food in my house.
Assuming I eat about 2000 calories per day, the per-calorie cost of this group of groceries suggests I will spend about $8/day on food. It is, of course, quite possible to eat more cheaply than this - even much more cheaply, depending on your willingness to make more food from scratch and/or eat the very cheapest boxed dinners and the like.
But $8/day appears to be about my comfortable average, under present circumstances.