TBH I've never really sat and worked it out but I do shop around for bargains and bulk buy stuff that's on offer. I breast feed so I don't need to buy formula or anything...although nappies work out quite a bit but with 10 people to do for something had to give.
Once a month or so I go out and spend about £250 on restocking the cupboards and freezer then I buy as and when we need things the rest of the time.....but saying that it's been a good few months since I did that and our cupboards are a bit bare (a la Mother Hubbard ).
_________________ I know my floor isn't clean enough to eat off, but then.....why would you want to?
we do our shopping every fortnight and it varies from around £120-£160 a fortnight. 2 adults and 3 kids. Jess is still in pull ups at night though, also depends whether or not I need washing powder etc as I think that bumps it up a bit, but I went to a market a few months back and got a massive load of persil tabs for £22. Have just run out though