Inventory Turnover Calculator
Enter the cost of goods sold for a period and your average inventory value, or the opening and closing values and the calculator averages them. You get turnover (how many times you sold through your stock) and days of inventory on hand. Nothing is sent anywhere.
In one sentence: Inventory turnover is how many times a period's cost of goods sold would use up your average stock; days on hand is how long that stock lasts.
Formula: turnover = COGS ÷ average inventory; days on hand = days in period ÷ turnover; average inventory = (opening + closing) ÷ 2.
What turnover tells you
Turnover measures how hard your stock is working. Four turns a year means the average item sits for about three months before it sells; twelve turns means about a month. Stock that sits is cash you cannot use and, for many products, value that fades through damage, obsolescence or seasonality. A rising turnover with stable sales usually means better buying; a falling one means stock is building up faster than it sells.
Measuring it properly
Use cost of goods sold, not revenue, because inventory is valued at cost; mixing the two inflates the ratio by your markup. Use the average inventory across the period rather than a single snapshot, which can be distorted by a delivery that arrived the day before you counted. The opening-and-closing option is the simplest average; if your stock swings a lot within the period, average monthly figures instead and enter the result directly.
Reading the number
There is no universal good value. Perishables and fast fashion turn many times a year; furniture and jewellery turn slowly by nature. Compare against your own history and against the lead time of your suppliers: days on hand far longer than the reorder lead time suggests you are ordering too much or too early, and ties up cash that the runway calculator would rather see in the bank.
Frequently asked questions
Can I use it for one product?
Yes. Use that product's cost of goods sold and its average stock value, and you get its own turnover and days on hand.
Does the period have to be a year?
No. Enter the number of days in whatever period your figures cover; days on hand adjusts accordingly.
Is my data stored?
No. Everything runs in your browser.