Look at the Turnover Rate
When looking at the number of seats in your restaurant, estimate how many times they can be turned overduring a shift. If you are a fine dining restaurant you may only get one seating during a dinner shift. A more casual establishments, such as a café or diner may get three or four seatings during dinner.
Understand Check Averages
Once you’ve estimated the number of guests at your restaurant at any given shift, you need to estimate the check average. Keep in mind that breakfast is typically the cheapest meal of the day, lunch is usually mid-priced and dinner is the most expensive. People are more apt to have a beer, wine or cocktail at dinner, helping to boost check averages further at dinner time. But people also have more time at dinner and so they may sit at the table longer, resulting in a smaller turnover rate.
Chart your estimated restaurant sales by month, to include in your restaurant business plan. Not only will help you with financing, it will give you a good idea of goals that you need to reach once your open, to make a profit and stay in business.
Once you have established your sales, next you need to establish your restaurant expenses.