Calculate days sales outstanding from your AR and credit sales. See days beyond terms, cash tied up in receivables, and what each day of improvement is worth.
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Short answer
To calculate DSO, divide accounts receivable by credit sales for the period, then multiply by the number of days in that period. With $1,240,000 of AR and $8,600,000 of quarterly credit sales over 91 days, DSO is 13.1 days. Compare the result to your payment terms — the difference is days beyond terms.
DSO tells you how long your cash sits inside someone else's business. It is the single most actionable working-capital number most finance teams have, because every day of improvement releases cash permanently and costs nothing to keep.
Enter your closing receivables and the credit sales for the same period. The calculator returns DSO, how far that sits beyond the terms you granted, the cash currently tied up in receivables, and what each day of improvement would release.
Your numbers
$
Trade AR net of credit notes. Exclude intercompany and non-trade balances.
$
Invoiced on terms only — cash and card sales must be excluded or DSO is understated.
days
Actual calendar days: 30/31 monthly, 90/91 quarterly, 365 annually.
Weighted average across customers if terms vary.
days
How many days of DSO you think you could remove.
Result
Days sales outstanding
13.1 days
Inside terms
Average daily credit sales$94,505
Days beyond terms-16.9 days
Cash tied up in receivables$1,240,000
Cash released by 2 days$189,011
Annualised credit sales (implied)$34,494,505
AR ÷ credit sales = $1,240,000 ÷ $8,600,000 = 0.1442
× 91 days in period
DSO = 13.1 days
Collections are inside terms. Protect this — watch billing lag and dispute rate before anything else.
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The formula
DSO = (Accounts receivable ÷ Credit sales) × Days in period
Accounts receivable
Closing trade AR for the period, net of credit notes. Exclude non-trade balances.
Credit sales
Revenue invoiced on terms during the period. Cash and card sales must be excluded.
Days in period
Actual calendar days — 30/31 for a month, 90/91 for a quarter, 365 for a year.
This is simple DSO, the reporting standard. If your monthly sales swing by more than about 30%, a countback calculation tracks real invoice ageing more faithfully.
Worked example
Accounts receivable
$1,240,000
Credit sales in period
$8,600,000
Days in period
91
Payment terms
Net 30
Result
DSO = 13.1 days · 0 days beyond terms
$1,240,000 ÷ $8,600,000 = 0.1442. Multiply by 91 days and DSO is 13.1 days — comfortably inside net-30 terms, so days beyond terms is zero. Average daily credit sales are $94,505, which is what one day of DSO improvement releases in cash.
Reading the result
DSO in isolation means very little — 45 days is excellent on net-60 terms and poor on net-15. Always read it against days beyond terms, which is the part of the delay you can actually recover.
Days beyond terms
What it usually means
Where to look first
Under 5
Healthy. Collections is working.
Protect it — watch billing lag and dispute rate.
5 to 15
Normal, with real cash still on the table.
Ageing worked by value; reminder ladder consistency.
Over 15
A process problem, not an effort problem.
Billing lag, invoice accuracy, unapplied cash, terms granted by sales.
Common mistakes that distort DSO
Including cash sales in the denominator. This is the most common error and it always flatters the result.
Using gross AR instead of AR net of credit notes, which overstates DSO and hides a credit-note backlog.
Assuming 30-day months — use actual calendar days or your monthly series develops a wobble that isn't real.
Mixing subsidiaries with different terms into one number, which averages a good business and a bad one into a meaningless middle.
Reading a single month. DSO is a trend metric; judge it over six periods or don't judge it at all.
Getting the inputs without a spreadsheet
The arithmetic takes seconds; assembling the inputs is what takes the afternoon — closing trade AR net of credit notes, credit sales with cash sales stripped out, split by subsidiary, for six periods. That is a saved search, an export and a pivot table in most ERPs.
With ERPray you ask for it: "DSO by subsidiary for the last six months, excluding cash sales" — computed live from your own account, with the query shown underneath so you can check the definition instead of trusting it.
Frequently asked questions
How do you calculate DSO?
Divide closing accounts receivable by credit sales for the period, then multiply by the days in that period. For example, $1.24M of AR against $8.6M of credit sales over 91 days gives 13.1 days. Use trade AR net of credit notes, and exclude cash sales from the denominator.
What is a good DSO?
One close to your payment terms. Days beyond terms under 5 is healthy, 5–15 is normal with room to improve, and over 15 usually indicates a billing or dispute problem rather than weak collections. Industry averages quoted without terms attached aren't useful comparisons.
What period should I use for DSO?
A month for operational tracking and a quarter or year for reporting. Shorter periods are noisier, especially with lumpy sales. Whichever you pick, keep the period length consistent and use actual calendar days rather than a rounded 30.
Why is my DSO higher than my payment terms?
Because invoices are being paid late, issued late, or disputed. The usual order of blame is billing lag first, invoice accuracy second, collections effort third. Best possible DSO — using only not-yet-due AR — separates the terms you granted from actual lateness.
Does DSO include VAT or sales tax?
Be consistent: if your AR balance includes tax then your sales figure should too. Most teams calculate DSO on tax-inclusive AR against tax-inclusive invoiced sales, because that's what actually has to be collected. Mixing the two bases produces a number that drifts for no real reason.
This calculator needs you to find the inputs first. ERPray pulls them from your own ERP account and computes the answer live — with the exact query shown so you can check it.