Inventory is money sitting on a shelf. The faster that money moves through your business, the less you tie up in warehousing, obsolescence, and markdowns — and the more efficiently you run. The inventory turnover ratio is the single number that tells you how many times you sold and replaced your stock in a period, and the days-in-inventory figure converts that ratio into the average number of days an item sits before it is sold.
This calculator takes three figures from your financial statements — your cost of goods sold (COGS), your beginning inventory, and your ending inventory — and instantly returns your average inventory, your turnover ratio, and your days in stock. Adjust any field and every result recalculates, so you can stress-test how a leaner buying plan or a seasonal surge would change the picture.
How to Use
- Enter your Cost of Goods Sold (COGS) for the period. This is the direct cost of the goods you actually sold — not your revenue, and not your purchases. Pull it from your income statement.
- Enter your Beginning Inventory, the cost of unsold stock you held at the start of the period. For a full-year analysis this is usually last year's ending inventory.
- Enter your Ending Inventory, the cost of unsold stock you counted at the close of the period. A physical count gives the most accurate number.
- Read the result card: Average Inventory first, then the highlighted Inventory Turnover Ratio, and finally Days in Inventory.
The engine first averages your beginning and ending stock to smooth out seasonal spikes: average inventory equals beginning inventory plus ending inventory, divided by two. It then divides COGS by that average to get how many times the stock turned over, and divides 365 by the ratio to express it in days.
The Inventory Turnover Formula
The formula is the standard efficiency ratio taught in accounting textbooks and used by analysts on Wall Street:
Inventory Turnover = COGS ÷ Average Inventory
where Average Inventory = (Beginning Inventory + Ending Inventory) ÷ 2.
And to express the result in days:
Days in Inventory = 365 ÷ Inventory Turnover
For example, if COGS is $1,000,000 and average inventory is $260,000, the turnover ratio is 3.85, meaning you sold and replaced your stock roughly 3.85 times in the year. Dividing 365 by 3.85 gives about 95 days in inventory — the average item sat on the shelf for around three months before selling.
Why use COGS instead of sales? Because inventory is carried at cost on the balance sheet. Dividing a cost figure by a cost figure keeps the units consistent. Using retail sales would inflate the ratio with your markup and make the number look better than it really is.
What a Good Turnover Ratio Looks Like
There is no universal "good" number because it depends entirely on your industry:
- Grocery and perishables turn over fast, often 10 to 15 times a year, because spoilage punishes slow-moving stock.
- General retail and e-commerce typically land between 4 and 6 turns annually.
- Furniture, jewelry, and luxury goods may turn only 1.5 to 3 times because each item is expensive and sells slowly.
A ratio that is too high can actually signal under-stocking and lost sales — if you turn over 14 times a year, you may be running out of popular items. A ratio that is too low means over-buying, slow-moving SKUs, and cash trapped in warehouse space. Compare your number to your own historical trend and to direct competitors, not to an arbitrary benchmark.
Examples
Example 1 — A typical retailer. A store reports COGS of $1,000,000, beginning inventory of $250,000, and ending inventory of $270,000. Average inventory is $260,000. The turnover ratio is 3.85 and days in inventory is 94.9 days — healthy, though there may be room to tighten buying.
Example 2 — The high-turnover grocer. A supermarket runs COGS of $4,000,000 with beginning inventory of $300,000 and ending inventory of $340,000. Average inventory is $320,000, giving a turnover ratio of 12.5 and just 29.2 days in stock. Fast movement keeps perishables fresh and cash flowing.
Example 3 — The overstocked boutique. A boutique has COGS of only $500,000 against a beginning inventory of $200,000 and a full ending inventory of $200,000. Average inventory is $200,000, so the ratio is 2.5 and days in inventory stretches to 146 days — more than four months of stock, a clear sign to discount slow SKUs and reorder less.
Example 4 — The scaled-up operation. A distributor with COGS of $5,000,000, beginning inventory of $1,200,000, and ending inventory of $1,300,000 averages $1,250,000 in stock, turning over 4.0 times a year for 91.25 days in inventory. The calculator handles figures of this magnitude without breaking a sweat.
FAQ
How do I calculate inventory turnover?
Divide your cost of goods sold by your average inventory, where average inventory is the sum of beginning and ending inventory divided by two. If COGS is $1,000,000 and average inventory is $260,000, your turnover is 3.85. This free calculator performs that division instantly once you enter the three figures.
What is a good inventory turnover ratio?
It depends on the industry. Grocers often run 10 to 15 turns, general retailers 4 to 6, and luxury or furniture stores 1.5 to 3. A ratio that is too low signals overstocking and tied-up cash; one that is unusually high can mean frequent stockouts and lost sales. Compare yourself to your own past performance and direct competitors.
Should I use sales or COGS to calculate turnover?
Use COGS. Inventory on the balance sheet is valued at cost, so dividing cost-of-goods-sold by average inventory keeps both sides of the equation in the same units. Using retail sales injects your markup and overstates how efficiently stock actually moves.
What does days in inventory mean?
Days in inventory is the average number of days an item sits in stock before it sells. It is calculated as 365 divided by the turnover ratio. A result of 95 days means the average product spends about three months in the warehouse before a customer buys it.
Why is average inventory used instead of ending inventory?
Because ending inventory at a single moment can be skewed by a seasonal spike or a year-end clearance. Averaging beginning and ending stock smooths out those swings and gives a more representative figure for the whole period. For even more precision, some analysts average quarterly inventory balances.
Why is my inventory turnover so low?
Common causes include over-ordering, poor demand forecasting, carrying slow-moving or obsolete SKUs, weak marketing, or pricing that is too high. Drill into your sales report by product line to find the worst offenders, then discount them, bundle them, or stop reordering them.
How can I improve my inventory turnover?
Tighten your forecasting and reorder points, cut low-performing SKUs, run targeted promotions on aging stock, use just-in-time ordering where possible, and align purchasing with actual sell-through data rather than guesswork. Even lifting the ratio from 3 to 5 frees up cash that was sitting on shelves.
Disclaimer
This inventory turnover calculator is provided for informational purposes only and does not constitute financial, accounting, or tax advice. Results are based on the figures you enter and the standard efficiency-ratio formula; actual turnover varies by accounting method, seasonality, and industry practice. Always consult a qualified accountant or financial advisor before making inventory or purchasing decisions.