Firstly, there is no standard percentage you should add to menu items.
Secondly, you need to:
- Calculate all overheads (e.g. wages, superannuation, tax, insurance etc.)
- Know the cost of goods (e.g. what you pay for one bottle of water; what you pay for each ingredient in a recipe)
- And then you can calculate the gross profit percentage using a formula. See the setting menu prices fact sheet for further information.