One challenge you face on a daily basis in business is calculating decision-making information when you know only part of the information. You must know how much you need to determine how changes in sales will affect the bottom line. If you know your fixed costs (FC), your variable costs per unit (VCu), your price per unit (P), and the number of units (U) sold, you can use a mathematical equation to determine your net income (NI). In this case the formula is: NI = [U * (P-VCu)] - FC