I am trying to put together a business plan for a restaurant but am confused about gross profit margins.  I understand that gross profit is whatever you have made after the cost of sale, but is this calculated against gross sales i.e. including VAT or against net sales excluding VAT?

Restaurants vary on what they try and achieve for their GP - anything between 65-75% seems to be the norm.  I'm just not sure if this is calculated to include VAT.

Feedback gratefully received.