Cash Conversion Cycle: Stock and Payment Terms

Calculate the three parts on the same basis

Days inventory outstanding (DIO) uses average inventory divided by cost of goods sold, multiplied by days in the period. Days sales outstanding (DSO) uses average trade receivables divided by credit sales, multiplied by days. Days payable outstanding (DPO) uses average relevant trade payables divided by credit purchases, multiplied by days.

Business Queensland's financial-ratio reference uses credit sales for debtor days and purchases on account for creditor days. Some reports use cost of goods sold as a proxy for purchases in DPO. Label that choice, especially when inventory changes materially. Don't compare a purchases-based result with a cost-of-sales result as if their methods were identical.

For a simple average, add opening and closing balances and divide by two. Monthly or daily averages can be more representative when balances swing widely. Keep the sales, inventory and supplier populations aligned; exclude unrelated debts. A zero denominator makes the relevant ratio undefined, not zero days.

Work through a 90-day example

Assumptions: AUD, GST-exclusive comparable balances. All sales and stock purchases are on credit. Period: 90 days; credit sales $180,000; cost of goods sold and credit purchases each $108,000. No seasonality or unrelated creditors.

Measure	Average balance	Calculation	Result
Inventory days	$54,000	$54,000 ÷ $108,000 × 90	45 days
Debtor days	$60,000	$60,000 ÷ $180,000 × 90	30 days
Supplier days	$36,000	$36,000 ÷ $108,000 × 90	30 days
Cash conversion cycle	Not a dollar balance	45 + 30 − 30	45 days

Original ASBG worked example. All businesses, amounts and scenarios are fictional. The table contains the same figures as the visual.

1. Stock held: 45 daysThe inventory stage comes before sale in this simplified cycle.
2. Customer collection: 30 daysThe sale is followed by the average collection period.
3. Supplier credit: subtract 30 daysSupplier terms offset part of the 75-day stock-and-collection period, leaving 45 days.

Xero's working-capital guide sets out the cycle formula: DIO + DSO − DPO. The measure is not specific to a tax jurisdiction; the example here uses Australian dollars and no UK tax rules.

Don't turn days into an exact funding figure

Multiplying 45 days by the example's $1,200 daily cost of sales gives $54,000, a rough cost-based timing proxy. It is not the actual inventory-plus-receivables-minus-payables balance. That balance is $78,000: $54,000 + $60,000 − $36,000.

The difference arises because receivables include the selling margin, while the daily cost measure doesn't. Full working capital also includes other current assets and liabilities. Use a dated cash forecast to establish actual payment needs; don't borrow an amount simply because a ratio suggests it.

Test an operational change

Reducing inventory days from 45 to 35, with the same daily cost, reduces average inventory from $54,000 to $42,000. The cycle falls to 35 days and $12,000 less is tied up in stock in this steady-state illustration. Cash is only released as purchasing and selling actually change.

Use the slow-stock worksheet to identify specific items. Improve debtor days through accurate invoices and collections. Any change to supplier terms needs agreement; overdue bills can make the ratio look better while the business is struggling to pay.

Watch what the average hides

A 30-day collection average can hide one large invoice that is seriously overdue. Seasonal buying can also make a quarter-end inventory balance unrepresentative. GST-inclusive debtors compared with GST-exclusive revenue can distort DSO. Ask whoever prepares your reports to document and repeat a consistent method.

Key takeaways

• Use the same period and matching balance populations for all three ratios.
• Separate a timing measure from actual dollars needed.
• Investigate the invoices and stock behind any change in the cycle.

Where to get help

Ask your accountant to check the report definitions against your balance sheet, particularly where purchases, creditor balances or seasonal averages are mixed.