How this calculator works
Standard DSO measures how many days of credit sales are sitting in receivables: DSO = (Accounts Receivable ÷ Credit Sales) × Days in Period. If you carry $850,000 of AR against $2.4M of quarterly credit sales, your DSO is about 32 days — on average, a dollar of revenue takes 32 days to become cash.
Best-possible DSO runs the same math using only current (not yet due) receivables. It answers a different question: if every customer paid exactly on time, what would DSO be? The spread between the two numbers is the part of DSO your collections execution controls — terms mix explains the rest.
Reading the results
The cash per DSO day figure is your period credit sales divided by days in the period. It converts DSO movement into money: a company doing $2.4M a quarter frees roughly $26,700 of cash permanently for every single day of DSO it removes. That is the number to put in front of a CFO when justifying investment in credit and collections operations.
Common mistakes when measuring DSO
Use credit sales, not total sales — cash sales in the denominator flatter the number. Keep the measurement window consistent (a 90-day quarter against quarter-end AR is the most common convention). And track best-possible DSO alongside standard DSO: teams that only watch the blended number often chase collections harder when the real driver is that sales keeps granting longer terms.
For the full set of reduction levers — billing accuracy, proactive reminders, prioritized worklists, dispute speed — see the DSO reduction playbook.