A valuation formula is used to determine what is the company worth. Here are 10 best calculations to help your business valuation.The Interactive Business Valuation Calculator can provide you with a rough idea of the value of your business. In this video I'm really going to be talking about the three core valuation methods and which one is the most applicable. It's based on seller's discretionary earnings (SDE). Rules of thumb for business valuation provide a quick method of estimating the value of small to medium size businesses. There are many formulas you can use. Determine the seller's discretionary earnings (SDE). This statement reflects your business's worth, which is vital for lenders assessing loan risks and for investors gauging value. Your business's value is measured in profits.