DSO & AR Aging Calculator

What is days sales outstanding (DSO)?

Days sales outstanding (DSO) is the average number of days it takes a business to collect cash after making a sale on credit. It converts the balance in accounts receivable into a time measure: how many days of credit sales are sitting uncollected right now.

DSO matters because receivables are cash you have earned but cannot spend. The same revenue with a lower DSO means more cash in the bank, less need for a line of credit, and less exposure to customers who never pay.

The formula

DSO = (accounts receivable ÷ credit sales for the period) × days in the period

• Use credit sales only. Cash sales are collected immediately and would understate DSO if included.
• Match the period: a quarter of credit sales goes with roughly 90 days, a year with 365.
• Average daily credit sales = credit sales ÷ days. Multiply by any change in DSO to see the cash impact — that is how the calculator's "every 5 days" figure is computed.

Worked example

Illustrative example — a hypothetical agency billing on net-30 terms, using one quarter:

1. Accounts receivable at quarter-end: $612,000.
2. Credit sales for the quarter: $1,530,000 over 90 days.
3. DSO = ($612,000 ÷ $1,530,000) × 90 = 0.40 × 90 = 36 days.
4. Average daily credit sales = $1,530,000 ÷ 90 = $17,000.
5. Bringing DSO from 36 days down to the 30-day terms frees 6 × $17,000 = $102,000 of cash.

Six days of slippage past terms looks small, but at this sales volume it is more than $100,000 sitting in customers' bank accounts instead of yours.

How to read your result

The most useful comparison is to your own payment terms. DSO close to your stated terms means customers are paying roughly on time; DSO well above terms means a meaningful share of receivables is late.

Trend beats level. A DSO that creeps up over several months usually signals a collections process problem or a customer in difficulty, even if the absolute number still looks reasonable.

DSO is an average and can hide a problem account. Pair it with an aging report: a few large invoices 90+ days past due can sit behind a healthy-looking DSO.

Industry norms differ widely with billing practices and terms, so compare yourself with businesses on similar terms rather than a generic benchmark.

Common mistakes

• Including cash sales. Cash sales were never in receivables, so including them in the denominator makes DSO look faster than it is.
• Using a period-end AR balance in a seasonal business. If the last month of the period was unusually large, period-end AR is inflated relative to the period's average sales. Use average AR or a shorter period that reflects current activity.
• Mismatched periods. Annual sales with 90 days, or quarterly sales with 365 days, produces a number that is wrong by a factor of about four.
• Treating unapplied cash and credit memos as collected. Payments sitting unapplied, or credits not matched to invoices, distort both AR and DSO. Clean them up before you measure.

Frequently asked questions

Further reading

• Revenue recognition without the headache — When revenue is recognized and when it is billed are different questions — and the gap shows up in receivables.
• Measuring ROI on finance technology (without fooling yourself) — How to measure whether a collections tool actually moved DSO.
• Upskilling your finance team for the AI era — Automation drafts the reminders; people still decide which accounts need a phone call.
• InflowWatch vs InvoiceSherpa — Two approaches to automating collections in QuickBooks.
• Collections on a connected ledger: turning AR aging into cash you can forecast — The collections routine behind a lower DSO.

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Worked examples on this page are illustrative and use hypothetical figures, not customer data. This page is general information, not lending, tax or investment advice.