Days Sales Outstanding (DSO) measures the average number of days it takes a business to collect payment after making a credit sale. It is the customer-facing counterpart to Days Payable Outstanding, and together with Days Inventory Outstanding, the two complete the cash conversion cycle.
FORMULA
Days Sales Outstanding = (Accounts Receivable ÷ Total Credit Sales) × Number of Days in Period
EXAMPLE
A distributor has $310,000 in accounts receivable and $2,400,000 in credit sales over a 90-day quarter.
DSO = ($310,000 ÷ $2,400,000) × 90 = 12 days.
On average, it takes about 12 days from a sale to collect payment.
Total credit sales, not total revenue, belongs in the denominator. Cash sales are already collected and should not be counted; including them understates DSO and makes collections look faster than they actually are.
A lower DSO means customers are paying faster, which improves cash flow and reduces the risk tied up in outstanding receivables. A rising DSO over time is one of the earliest warning signs of either loosening credit standards, deteriorating customer financial health, or a collections process that has stopped being followed consistently.
DSO should always be read against a business's own stated payment terms. A DSO of 35 days looks fine against net 30 terms, since some lag between due date and actual payment is normal, but the same 35 days against net 15 terms means customers are taking more than double the agreed period to pay.
FORMULA
Cash Conversion Cycle = DIO + DSO − DPO
DSO is the second input, representing how long cash stays tied up in receivables after inventory has already sold. It combines with DIO, how long inventory sat before that sale, and DPO, how long the business takes to pay its own suppliers, to give the complete picture of the operating cash cycle.
EXAMPLE
A distributor with 61 days DIO, 45 days DSO, and 30 days DPO has a cash conversion cycle of 61 + 45 − 30 = 76 days. Cutting DSO from 45 to 30 days through tighter collections shortens the cycle by 15 days, the same effect as extending supplier payment terms by two weeks, without touching a single vendor relationship.
DSO is fundamentally a sales and collections metric, but it belongs in the same conversation as DPO because both draw from the same limited pool of working capital, and a business that ignores one while optimizing the other is only solving half the problem.
