revenue. This consists of the total dollars from sales activity that you bring into your business each month, week or year. Fixed costs. These are sometimes called "overhead" and you must pay them regardless of how well you do. Fixed costs dont vary much from month to month. They include rent, insurance and other set expenses.     Gross profit for each sale. This is defined as how much is left from each sales dollar after paying for the direct costs of that sale. For example, if Antoinette pays $100 for a dress that she sells for $300, her gross profit for that sale is $200.     Break-even sales revenue. This will be the dollar amount your business needs each week or month to pay for both direct product costs and fixed costs. It will not include any profit.     WarningMath alert: The following section requires that you make some simple mathematical calculations, which youll use to analyze your business before writing a complete plan. If the very thought of math makes your head spin, youll probably want to find someone to help you.     1. Forecast Sales Revenue     Your first task is to estimate your most likely sales revenue by month for your first two years of operation. This is both the hardest thing to do and the most important part of your business plan. Much of your hope for success rides on how accurately you estimate sales revenue.     Keep in mind that youre honestly trying to decide if your business will be profitable. This means that you must base your forecast on the volume of business you really expect-not on how much you need to make a good profit. If you estimate sales too high, your business wont have enough money to operate. But if you estimate sales too low, you wont be prepared or able to handle all the business you get.     Appendix 4 contains a Sales Revenue Forecast form, where you can fill in your estimated two-year monthly sales revenue. Depending on the type of business, you may also choose to fill in the number of units you expect to sell. Here are some methods different types of businesses use to forecast sales revenues.     NoteYou may decide to round off your forecasts to the nearest $1,000 instead of writing out each single dollar amount. For instance, a monthly sale of $33,333 would become $33,000. After all, these are guesses, and its hard to guess at single dollar amounts when youre in the five-figure area.     a. Retail Sales Revenue Forecast     The simplest way to forecast retail sales revenue is to find the annual sales revenue per square foot of a comparable store. Then multiply that dollar figure by your estimated floor space to derive an estimate of your annual sales revenue.     Example: A similar business shows $200 of sales per square foot per year. If you have 1,000 square feet of floor space, your estimated annual sales revenue will be $200,000 (1,000 x $200). Naturally, your estimate should take into account everything that makes you different from the other store.