TL;DR: Inventory turnover is cost of goods sold divided by average inventory for the period. Illustrative example only: a company with cost of goods sold of $1,200,000 and average inventory of $300,000 turns its inventory 4.0 times a year, since $1,200,000 divided by $300,000 equals 4.0. The same figure as days is 365 divided by 4.0, which equals 91.25 days of stock on hand on average. Higher turnover means stock moves faster, but the healthiest level for a grocer and the healthiest level for a furniture maker are completely different numbers.
Key Takeaways
- The numerator is cost of goods sold, not revenue, because inventory is carried at cost and the two must be measured on the same basis.
- Average inventory, usually opening plus closing divided by two, smooths the year end snapshot, which can be unusually high or low.
- Days inventory is the same information in a more intuitive unit: 365 divided by the turnover figure.
- Turnover is only comparable inside similar businesses. Seasonality, perishability, and product value change what good means.
Work the example in full
All figures in this section are illustrative. A retailer reports cost of goods sold of $1,200,000 for the year. Its inventory was $280,000 at the start of the year and $320,000 at the end. Average inventory is $280,000 plus $320,000, which equals $600,000, divided by 2, which equals $300,000. Turnover is $1,200,000 divided by $300,000, which equals 4.0. In words: the stock the retailer holds at a typical moment sold through and was replaced about four times during the year.
Convert it to days for the version most operators actually think in. Days inventory is 365 divided by 4.0, which equals 91.25 days. Check it the other way: average inventory of $300,000 divided by daily cost of goods sold gives the same figure, since $1,200,000 divided by 365 equals about $3,287.67 per day, and $300,000 divided by $3,287.67 equals about 91.25 when rounded. Both routes agree, as they must, because days inventory is only turnover restated.
Why average instead of the closing balance? Because a single date can mislead. A retailer who stocks up before a peak season shows swollen closing inventory and an unfairly low turnover if only that snapshot is used, while one who runs stock down before year end looks artificially efficient. Averaging opening and closing balances is the simple fix, and some analysts average quarterly balances for seasonal businesses, going further in the same direction. The raw inputs, inventory and cost of goods sold, are found using how to read a balance sheet and how to read an income statement.
Reading the number without fooling yourself
Very low turnover can mean stock is sitting, ageing, and heading toward discounts or write offs, tying up cash that the free cash flow yield explained side of analysis will eventually miss. Very high turnover is not automatically excellent either: it can mean the shelves run empty, sales are lost to stock outs, and the business is one delayed delivery away from an empty shop. The ratio flags the question, and the business model supplies the answer. Perishable goods demand high turnover by nature. Durable, high value goods turn slowly by nature. Comparing a supermarket chain with a jeweller on this ratio compares their industries, not their management.
Turnover also connects to the efficiency family alongside asset turnover ratio explained, which asks the same sell through question about all assets rather than inventory alone. Read together, they show whether slowness lives in the stockroom or across the whole asset base. Read over several years, a drifting turnover trend inside one company is usually more informative than any single comparison against another company, because the business model is held constant and only the execution moves.
One measurement caution: a change in accounting method, a shift toward drop shipping, or a move between owning stock and holding it on consignment can all move the ratio without any change in how well the shops are run. When turnover jumps suddenly, check what changed in the business before crediting or blaming operations.
This article is educational information about how the inventory turnover ratio is calculated, not financial advice. Figures in the worked example are illustrative and are not the results of any real company.
Sources and method
- Target keyword: "inventory turnover ratio explained" from .saeo/keywords.yaml (queue entry added 2026-10-30). No search volume or difficulty figure is claimed; both are recorded as unknown in the queue entry.
- All figures are labelled illustrative examples. Arithmetic verified for this draft on 2026-10-30: $280,000 plus $320,000 equals $600,000; $600,000 divided by 2 equals $300,000; $1,200,000 divided by $300,000 equals 4.0; 365 divided by 4.0 equals 91.25; $1,200,000 divided by 365 equals $3,287.67 rounded to cents; $300,000 divided by $3,287.67 equals 91.25 when rounded to two decimals.
- Internal links checked against existing drafts in this folder on 2026-10-30: how-to-read-a-balance-sheet, how-to-read-an-income-statement, free-cash-flow-yield-explained, asset-turnover-ratio-explained.
- Note on link timing: asset-turnover-ratio-explained was drafted in the same 2026-10-30 run and sits in this same drafts folder.
