Inventory is cash sitting on a shelf. Inventory turnover tells you how many times a year that cash cycles through sales, and days sales of inventory (DSI) tells you how long a typical item waits before it sells. Together they show whether you’re carrying too much stock — and how much money you could free up by carrying less.
How to use the inventory turnover calculator
- Choose whether to measure with cost of goods sold (recommended) or net sales.
- Enter COGS or sales for the period, plus beginning and ending inventory at cost.
- Choose the period length: a year, a quarter, a month or a custom number of days.
- Optionally set a target annual turnover and your carrying cost to see the cash and cost savings of leaner inventory.
Inventory turnover formulas
For a quarter or month, the calculator also annualizes turnover by scaling COGS to 365 days, so periods of different lengths can be compared. If inventory swings a lot during the year, averaging month-end balances gives a truer average than just the opening and closing figures.
Worked example
A hardware store had $90,000 of inventory at the start of the year and $110,000 at the end, with $500,000 of cost of goods sold.
Average inventory = (90,000 + 110,000) ÷ 2 = $100,000
Turnover = 500,000 ÷ 100,000 = 5.0× a year
DSI = 365 ÷ 5 = 73 days
The owner wants to reach 6 turns a year. That requires an average inventory of 500,000 ÷ 6 = $83,333, freeing about $16,667 of cash. With carrying costs of 25% a year — storage, insurance, shrinkage, obsolescence and the cost of money — that is roughly $4,167 a year in savings.
Why turnover matters
| Turnover trend | What it can mean |
|---|---|
| Rising | Leaner stock, better buying, stronger sales — or a growing risk of stockouts |
| Falling | Slow-moving or obsolete items, over-ordering, or sales falling short of plan |
| Much higher than peers | Efficient operations, or too little safety stock |
| Much lower than peers | Cash tied up in inventory that may need markdowns |
Ways to improve inventory turnover
- Find the slow movers. Run turnover by product line or SKU; a few items often hold a large share of the stock.
- Order smaller and more often when suppliers allow, especially for predictable items.
- Clear aging stock with markdowns before it becomes obsolete — use the markup calculator to see how much margin you can give up.
- Forecast with real sales data rather than rules of thumb, and set reorder points per item.
Inventory turnover is one of several efficiency measures. The efficiency ratios calculator adds receivables and payables to show the full cash conversion cycle.
Results are estimates for analysis and planning, not accounting or financial advice. Use inventory valued consistently (FIFO, LIFO or average cost) across periods.
Frequently asked questions
How do you calculate inventory turnover?
Divide cost of goods sold for the period by average inventory, where average inventory is usually the beginning balance plus the ending balance divided by two. $500,000 of COGS with $100,000 of average inventory is a turnover of 5 times a year.
What is days sales of inventory (DSI)?
DSI converts turnover into days: the number of days in the period divided by turnover. A turnover of 5 a year means inventory sits about 73 days on average before it is sold. Lower DSI means cash comes back faster.
Should I use COGS or sales to calculate turnover?
COGS is preferred because both COGS and inventory are recorded at cost. Using sales mixes in your markup and inflates the ratio. Use the sales version only to compare with a benchmark that was calculated that way.
What is a good inventory turnover ratio?
It depends heavily on the industry. Perishable goods and grocery move many times a year, while furniture, jewelry or heavy equipment may turn only a few times. Compare with similar businesses and with your own trend: rising turnover usually means leaner stock, but turnover that is too high can mean frequent stockouts.