Operations Ratios Calculator: Inventory, DSO & Cycle Time

How the operations ratios work

The five ratios all answer one question: how long is cash tied up in the operation? Inventory turnover is COGS divided by average inventory — $600,000 ÷ $100,000 is 6.00 times a year — and it says the stock is sold and replaced six times a year. DIO, days inventory outstanding, is 365 divided by turnover — 365 ÷ 6.00 is 60.83 days — and it says a typical item sits on the shelf for about two months before it sells. DSO, days sales outstanding, is accounts receivable divided by revenue, times 365 — $120,000 ÷ $1,000,000 × 365 is 43.80 days — and it says customers take about six weeks to pay. Asset turnover is revenue divided by total assets — $1,000,000 ÷ $800,000 is 1.25 times — and it says each dollar of assets generates $1.25 of sales a year. The operating cycle is DIO plus DSO — 60.83 + 43.80 is 104.63 days — and it says cash is tied up for about three and a half months between buying the stock and collecting the sale. Receivables turnover, the secondary output, is revenue divided by accounts receivable — $1,000,000 ÷ $120,000 is 8.33 times — and it is the flip side of DSO: 365 ÷ 8.33 is the same 43.80 days.

The worked example, line by line

Setup: revenue $1,000,000, COGS $600,000, average inventory $100,000, accounts receivable $120,000, total assets $800,000.

Line 1 — inventory turnover. $600,000 ÷ $100,000 = 6.00×.

Line 2 — DIO. 365 ÷ 6.00 = 60.83 days.

Line 3 — DSO. $120,000 ÷ $1,000,000 × 365 = 43.80 days.

Line 4 — asset turnover. $1,000,000 ÷ $800,000 = 1.25×.

Line 5 — operating cycle. 60.83 + 43.80 = 104.63 days.

Line 6 — receivables turnover. $1,000,000 ÷ $120,000 = 8.33×.

Branch — retailer: turnover $1,500,000 ÷ $150,000 = 10.00×; DIO 365 ÷ 10.00 = 36.50 days; DSO $50,000 ÷ $2,000,000 × 365 = 9.13 days; asset turnover $2,000,000 ÷ $1,000,000 = 2.00×; cycle 36.50 + 9.13 = 45.63 days.

Branch — manufacturer: turnover $3,000,000 ÷ $750,000 = 4.00×; DIO 365 ÷ 4.00 = 91.25 days; DSO $600,000 ÷ $5,000,000 × 365 = 43.80 days; asset turnover $5,000,000 ÷ $4,000,000 = 1.25×; cycle 91.25 + 43.80 = 135.05 days.

Branch — slow stock: turnover $400,000 ÷ $400,000 = 1.00×; DIO 365 ÷ 1.00 = 365.00 days; DSO $200,000 ÷ $800,000 × 365 = 91.25 days; asset turnover $800,000 ÷ $1,200,000 = 0.67×; cycle 365.00 + 91.25 = 456.25 days.

Branch — cash-only: turnover $250,000 ÷ $50,000 = 5.00×; DIO 365 ÷ 5.00 = 73.00 days; DSO $0 ÷ $500,000 × 365 = 0.00 days; asset turnover $500,000 ÷ $300,000 = 1.67×; cycle 73.00 + 0.00 = 73.00 days.

Operations ratios by business type

The table shows why the ratios must be compared inside an industry, not across one: a retailer turns stock 10.00 times a year with a 45.63-day cycle, while a manufacturer turns it 4.00 times with a 135.05-day cycle — and both can be healthy. What matters is the direction over time and the distance from the industry norm. The slow-stock row is the warning: stock that turns once a year ties cash up for 456.25 days, more than fifteen months from purchase to collection.

Rounding convention, stated plainly: turnover ratios are shown to two decimals, days to two decimals, and the operating cycle is the sum of the unrounded DIO and DSO, rounded to two decimals — so 60.83 + 43.80 is exactly 104.63, and 36.50 + 9.13 is exactly 45.63. DSO of 9.13 days comes from the unrounded 9.125, rounded up to two decimals.

Output · formula · meaning

Who uses this

• The small retailer: turns stock 10.00 times a year with a 36.50-day DIO and a 9.13-day DSO, and learns the operating cycle is only 45.63 days — cash comes back in six weeks, so the shelves can be restocked fast and the business can grow on its own cash.
• The manufacturer: holds raw materials and work in progress, turns stock 4.00 times a year with a 91.25-day DIO, and learns the operating cycle is 135.05 days — cash is tied up for four and a half months, so the credit line has to cover that gap.
• The owner with slow stock: sees turnover of 1.00 times a year and a DIO of 365.00 days, and learns the operating cycle is 456.25 days — more than fifteen months from purchase to collection — which is the signal to discount the slow lines and stop reordering them.
• The cash-only shop: has no receivables at all, so DSO is 0.00 days and the operating cycle is just the 73.00-day DIO — and learns that every day shaved off the shelf time is a day of cash freed, because there is no collection delay to hide behind.

Accuracy & limitations

The math is exact for the numbers you enter: turnover is COGS divided by average inventory, DIO is 365 divided by turnover, DSO is receivables over revenue times 365, asset turnover is revenue over assets, and the operating cycle is DIO plus DSO. But the inputs carry the assumptions: average inventory should be the average of opening and closing inventory, not the year-end figure alone — a business that stocks up in December will show a worse DIO on the year-end number. The 365-day year is the convention; some analysts use 360. DSO uses year-end receivables, which flatters a business whose receivables spike at year end and understates one that collects steadily. The operating cycle also leaves out the other side of the cash conversion cycle — days payable outstanding, the time the business takes to pay its own suppliers — so it measures how long cash is tied up, not how long the business has to fund it. Compare these ratios inside one industry and over time, never across industries: a retailer at 10.00 times and a manufacturer at 4.00 times can both be healthy. This is an educational tool, not financial advice.