DSO is a measure of the number of days that it takes to collect on accounts receivable.Remember,if you do business in cash,then your DSO is zero,but if you sell on credit,then this will be a positive number.DSO is calculated using the following equation: DSO = Average Accounts Receivable/Revenue per day Average Accounts Receivable = (Beginning Accounts Receivable + Ending Accounts Receivable)/2 Revenue per day = Revenue/365