DSO Calculator (Standard & Countback)

How to use it

Enter what customers owed you at the end of the latest month, the credit sales for each of the last three months, and your usual payment terms. The calculator works out days sales outstanding two ways, the standard average and the countback credit controllers use, and how much of the balance is older than your terms.

Where the number comes from

• Standard DSO = receivables ÷ the three months’ credit sales × the days in those three months.
• Countback DSO starts with the most recent month: if receivables exceed that month’s sales, the whole month counts and its sales are subtracted. It repeats with the month before until what is left is less than a month’s sales.
• The last, partly matched month counts as what is left ÷ that month’s sales × the days in the month. DSO is the sum of the days counted.
• Days beyond terms = countback DSO − payment terms.
• Cash tied up beyond terms = receivables − the sales made within the terms window (newest first), which is each month’s daily sales × the days beyond terms that fall in it.
• Average daily credit sales = the three months’ credit sales ÷ the days in them.

What goes wrong

The part most calculators leave out.

• Cash sales mixed into the sales figures make DSO look shorter than it is. Use only sales invoiced on terms.
• If receivables include sales tax but the sales figures do not, DSO comes out too long by roughly the tax rate. Use the same basis on both sides.
• A single month-end snapshot can be flattered by a big collection push in the last week. Track the figure month after month rather than reading one.
• DSO is an average. A healthy DSO can hide one large customer far overdue; an aged-debt report shows what the average cannot.
• Unapplied cash and credit notes left unmatched distort the receivables balance. Clean the ledger before measuring.

Questions

Why do the standard and countback methods give different DSO?

The standard method divides receivables by an average of the period’s sales. Countback matches receivables against actual months, newest first, so it reflects the sales that created the balance. When sales are steady the two agree; when they swing, countback is the one that follows reality.

Which DSO method should I report?

Whichever you use consistently. Countback is preferred by many credit controllers because seasonal sales do not distort it as much, but a trend in either method tells you more than a single figure in both.

What does it mean when receivables exceed three months of sales?

The countback runs out, so DSO is over 3 months. Part of the balance is older than any sale entered, which usually points to disputed, forgotten or doubtful invoices.

Does anything I type get sent anywhere?

No. The whole calculation runs in your browser. Nothing is sent to us or logged, and there is no account to create. Your browser keeps the figures with this tab’s history so that Back and Reload bring them back, and Reset clears them.