Inventory turnover measures how many times you sell through and replace your average stock in a year. The accurate, cost-basis formula is inventory turnover ratio = cost of goods sold (COGS) / average inventory at cost, where average inventory = (beginning inventory + ending inventory) / 2. From that you also get days sales of inventory (DSI) = 365 / turnover ratio, the average number of days it takes to sell your stock. Enter your three figures in the calculator below to get both, and read on for the worked example.
A free tool to see how fast your money is moving through stock, and roughly how long a unit sits before it sells.
Every unit on your shelf is cash you have already spent and not yet earned back. Inventory turnover is the simplest way to see how hard that cash is working: how many times over the year you sell through the stock you typically hold and buy it again. A high turnover means money is cycling through quickly; a low one means it is sitting still, tied up in goods that are aging on the shelf. The companion number, days sales of inventory, turns the ratio into something more intuitive, the average number of days a unit waits before it sells.
Most people who reach for a turnover calculator want their own figure rather than a definition, so the tool comes first and the explanation second. There is also an honest section below on what a “good” ratio actually depends on, and why a single number in isolation tells you less than you might think.
Inventory turnover calculator
What is inventory turnover and how is it calculated?
Inventory turnover answers one question: how many times in a year did I sell through and replace my average level of stock? You work it out by comparing what it cost you to sell everything you sold over the year against how much stock you typically held to do it.
The accurate, cost-basis formula is:
Inventory turnover ratio = cost of goods sold (COGS) / average inventory at cost
where
Average inventory = (beginning inventory + ending inventory) / 2
The three inputs are:
- Cost of goods sold (COGS) — the total cost of the goods you sold over the period, at cost, not at their selling price. For a year, that is your annual COGS.
- Beginning inventory value — the value of your stock at the start of the period, at cost.
- Ending inventory value — the value of your stock at the end of the period, at cost.
Averaging the beginning and ending values smooths out the swing between a full shelf and a picked-over one, so the ratio reflects a typical stock level rather than a single day’s snapshot. If your stock is very seasonal, an average of monthly balances is more honest still, but for most businesses the two-point average is close enough.
Why COGS and not sales
You will see turnover defined two ways: some use sales / average inventory, others use COGS / average inventory. The COGS version is the accurate one, and it is the version this calculator uses, because both parts of the ratio are then measured at cost. Sales include your markup, while your inventory sits on the books at cost, so dividing sales by inventory mixes a retail number over a cost number and inflates the ratio. Comparing cost against cost keeps the two sides on the same footing. Qoblex’s guide to the inventory turnover ratio uses the same COGS-over-average-inventory formula.
Worked example, step by step
Say over the year your cost of goods sold was $1,000,000. You started the year holding $150,000 of stock at cost and finished it holding $250,000. So COGS = $1,000,000, beginning inventory = $150,000, and ending inventory = $250,000.
First find the average inventory:
- Average inventory = ($150,000 + $250,000) / 2 = $200,000
Then the turnover ratio:
- Turnover ratio = $1,000,000 / $200,000 = 5.0 times per year
Then days sales of inventory:
- DSI = 365 / 5.0 = 73 days
So you sold through and replaced your average stock five times over the year, and on average a unit sat for about 73 days before it sold. Load these figures into the calculator above and you should land on exactly those numbers.
What counts as a “good” turnover ratio?
This is the part where a single number can mislead you, so it is worth being plain: there is no universal “good” turnover ratio. What is healthy depends heavily on what you sell and how you sell it, and comparing your figure to someone else’s without that context is how people talk themselves into the wrong decision.
Two things move the goalposts more than anything else:
- Your industry. Fast-moving, low-margin goods like fresh food or fashion basics are expected to turn many times a year, because the whole model depends on velocity. Slow-moving, high-margin goods like furniture, jewellery, or specialist equipment turn far fewer times, and that is fine, because each sale earns much more. A ratio that looks alarming in one category is perfectly normal in another.
- Your margins. A business running thin margins needs high turnover to make the model work; a business with fat margins can afford to hold stock longer. So turnover has to be read alongside margin, not on its own.
Rather than chase an arbitrary target, the more useful move is to compare your own ratio over time, and line by line. A turnover that is falling quarter on quarter, or a handful of SKUs turning far slower than the rest, tells you more than any single blended figure, because it points you at the specific stock that is tying up cash or heading toward obsolescence. Turnover is a direction indicator, best read as a trend and at the SKU level, not a score to hit.
The DSI figure the calculator returns is the same idea from the other direction: days rather than turns. For how to read DSI and how it tends to vary by industry, see our guide to days sales of inventory.
From the number to the decision
Turnover tells you how fast stock is moving. It does not, on its own, tell you what to do next, and that is usually the more useful question. A low turnover on a particular line is a prompt to look at how much you order and when, so the natural companions to this tool are the ones that act on the number:
- How much to order in one go, so you are not constantly reordering or overbuying: your economic order quantity.
- When to place the next order given your lead time: your reorder point.
- How much buffer to hold against demand and lead-time surprises: your safety stock.
Read turnover as the symptom, and use those three to adjust the cause: the quantities and timing behind the stock that is moving too slowly or too fast.
How Qoblex fits in
The calculator above is a check you run by hand. Qoblex does not replace that reading, and the honest framing is this: the reason turnover is a chore to calculate is usually that the three numbers live in different places, your COGS in the accounting ledger, your inventory value in a stock sheet, your sales history somewhere else again. Qoblex keeps those figures in one place. Because it costs your stock with a perpetual moving average, the COGS behind each sale and your current inventory value are maintained as you trade, alongside the sales history the ratio draws on, so you can pull the inputs without stitching a spreadsheet together first.
Your accounting platform stays your book of record: Qoblex handles the operational inventory and costing while QuickBooks Online or Xero keeps the ledger. For current plans, see qoblex.com/pricing.
FAQ
What is inventory turnover? Inventory turnover is the number of times you sell through and replace your average level of stock over a period, usually a year. A higher ratio means stock is moving quickly and cash is cycling; a lower one means stock is sitting longer and more cash is tied up in it.
What is the inventory turnover formula? Inventory turnover ratio = cost of goods sold (COGS) / average inventory at cost, where average inventory = (beginning inventory + ending inventory) / 2. Both parts of the ratio are measured at cost so they are on the same footing.
What is days sales of inventory (DSI)? DSI is the average number of days it takes to sell through your stock. You get it from the turnover ratio: DSI = 365 / turnover ratio. If your turnover is 5.0, your DSI is 365 / 5 = 73 days.
Should I use sales or COGS in the turnover formula? Use COGS. Sales include your markup while inventory sits on the books at cost, so dividing sales by inventory mixes a retail figure over a cost figure and inflates the ratio. COGS over average inventory compares cost against cost, which is the accurate version.
What is a good inventory turnover ratio? It depends on your industry and your margins, so there is no universal target. Fast-moving, low-margin goods are expected to turn many times a year; slow-moving, high-margin goods turn far fewer times, and that can be perfectly healthy. Comparing your own ratio over time and at the SKU level is more useful than chasing a benchmark.
Why is my average inventory the average of beginning and ending stock? Averaging the start and end values smooths out the swing between a full shelf and a depleted one, so the ratio reflects a typical stock level rather than a single day’s snapshot. If your stock is highly seasonal, averaging monthly balances gives a more accurate figure.