The formula
Inventory turnover equals cost of goods sold divided by average inventory. Average inventory is the value at the start of the period plus the value at the end, divided by two. If your cost of goods sold for the year is $60,000 and your inventory went from $10,000 to $14,000, the average is $12,000 and turnover is five.
That means you sold through your stock about five times in the year.
Days of inventory on hand
Divide the days in the period by the turnover to see how long a typical item sits before it sells. Using 365 days and a turnover of five gives about 73 days.
Days on hand is often easier to act on than a ratio. It translates directly into how much cash is sitting on shelves and how far ahead you are buying.
Why use cost, not sales
Inventory is recorded at cost, so cost of goods sold is the matching figure. Using sales instead would mix in your markup and overstate turnover. Make sure your cost of goods sold includes only what you actually sold, and that your inventory count is accurate, since a miscounted shelf distorts everything.
If your books record inventory only at year end, calculate with year-end values, and use a physical count for the number.
Reading the number
Higher is not always better. A high turnover can mean efficient buying, or it can mean you often run out of popular items and lose sales. A low turnover ties up cash and risks items going stale, damaged or out of style.
There is no single right answer. Compare your number to your own past periods and to businesses that sell similar goods, and look at it by product category when you can, because a few slow items often hide behind a healthy average.
A worked example by category
Suppose a shop sells three kinds of goods. Seasonal gifts turn four times a year, everyday supplies turn twelve times, and a line of specialty items turns only once. The blended average looks fine, but the specialty line holds a large share of the cash for a full year.
Looking at turnover by category shows where to cut buying, where to reorder sooner and where a higher margin justifies the slower pace. Check each line on a regular schedule, and recount stock before making big decisions.
What to do with it
If days on hand is growing, check for overbuying, slow sellers and items bought in bulk for a discount that never paid off. Consider clearance pricing, bundles or smaller, more frequent orders.
If stockouts are the problem, look at reorder points for your fastest sellers. Pair turnover with gross margin, because a slow item with a high margin can still be worth carrying. A free calculator can speed up these comparisons across periods.
Common questions
Can service businesses use inventory turnover?
Not usually. It applies to businesses that hold goods for sale. Service businesses can look at receivables and billable time instead.
Which inventory method should I use?
Use the method your books and tax filings already follow, and keep it consistent. Ask your tax preparer before changing it.
How often should I calculate it?
Monthly or quarterly is common, and it matters most before big buying seasons.
This guide is general information, not tax, legal or accounting advice. Rules, fees and due dates change; check with the IRS, the NJ Division of Taxation or a licensed professional for your situation.