Inventory Turnover Ratio: Formula, Calculation and Example
The inventory turnover ratio is cost of goods sold divided by average inventory. Here's the formula, a worked example for a small-batch manufacturer, and how to read the number.
Most small manufacturers can tell you what they sold last month. Fewer can tell you how long their money sat on a shelf first.
That’s what the inventory turnover ratio measures: how many times a year you sell through your stock and buy it again. You’ll also see it called inventory velocity, stock turn or inventory turns. They usually mean the same ratio.
Here’s the formula, a step-by-step calculation, a worked example for a small-batch skincare brand, and how to tell whether your number is a problem or just a number.
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What is the inventory turnover ratio?
Inventory turnover ratio is cost of goods sold divided by average inventory value, showing how many times you sell through and replace stock.
A ratio of 4 means you sold the equivalent of your average stock four times during the period. The higher the ratio, the less cash is parked on your shelves. The lower it is, the longer stock sits between arriving and leaving.
If you make what you sell, “stock” means three things, not one: raw materials and packaging, work in progress, and finished goods. Our guide to manufacturing inventory management covers each. The ratio blends all three, which is why it’s worth splitting them later in this guide.
The inventory turnover formula
Inventory turnover ratio = Cost of goods sold ÷ Average inventory value
Average inventory value = (Opening inventory value + Closing inventory value) ÷ 2
Two inputs, both measured over the same period.
Cost of goods sold (COGS) is what it cost you to make the products you sold: the materials, and any hired labour, that went directly into them. If you haven’t pinned that down yet, start with how to calculate COGS.
Average inventory value is everything you’re holding, at cost: raw materials, packaging, work in progress and finished goods. Add the value at the start of the period to the value at the end, then divide by two. How you value stock changes the number, so pick a costing method and stick with it.
Count the same costs in both numbers. If COGS includes hired labour but your stock value only counts materials, the ratio comes out too high. Pick a basis and use it for both.
Use cost, not revenue. Some sources divide sales by inventory instead. That mixes a price-based number with a cost-based one and inflates the ratio by your markup, so it won’t compare with a cost-based figure.
If your stock swings with the season, two data points can distort the picture. Average your month-end values instead: add the twelve and divide by twelve.
How to calculate inventory turnover in five steps
- Pick a period. A year is standard. A quarter works if you want to see seasonal swings. Use the same period for both inputs.
- Get COGS for that period. Pull it from your accounting system or your costing records.
- Get inventory value at the start and end of the period. Count every type of stock, at cost.
- Average the two values. Or average twelve month-ends if your year is lumpy.
- Divide COGS by average inventory. To turn the ratio into days, divide the days in your period by it (365 for a year). That’s your days of inventory on hand.
Keep the period consistent. A monthly ratio is about a twelfth of the annual one, so multiply it by 12 before you compare it with an annual benchmark.
A worked example for a small-batch manufacturer
Say you run a small-batch skincare brand that makes serums and balms in batches of a few hundred units. Here are your numbers for the year (illustrative figures):
| Input | Figure |
|---|---|
| COGS for the year | $420,000 |
| Inventory value on 1 January | $95,000 |
| Inventory value on 31 December | $115,000 |
| Average inventory value | $105,000 |
| Inventory turnover ratio | 4.0 |
| Days of inventory on hand | 91 |
Average inventory is ($95,000 + $115,000) ÷ 2 = $105,000. Divide $420,000 by $105,000 and you get 4.0. Divide 365 by 4.0 and you get about 91 days.
In plain terms, the average dollar tied up in stock waits about three months to sell.
As a check on the monthly version, $35,000 of COGS a month over the same $105,000 gives 0.33, and 0.33 × 12 is 4.0.
Where the 91 days are sitting
One number can’t tell you where the cash is stuck. Split the average by stock type, then divide each by daily COGS ($420,000 ÷ 365, about $1,151 a day). The three shares add up to the 91:
| Stock type | Average value | Days (share of the 91) |
|---|---|---|
| Raw materials and packaging | $48,000 | 42 |
| Work in progress | $7,000 | 6 |
| Finished goods | $50,000 | 43 |
| Total | $105,000 | 91 |
Now the number says something you can act on. Materials and finished goods hold about the same cash, so there are two places to look: what you buy ahead of need, and what you build ahead of demand.
Before you judge the materials, measure them against what you actually use. The 42 days above is measured against total COGS, which includes hired labour. If materials are about 70% of COGS, you use roughly $800 of them a day, so $48,000 on hand is about 60 days.
Now compare that with how you reorder. Between deliveries a material runs down from a full order plus your safety stock to just the safety stock, so on average you hold roughly half an order plus the safety stock. Order monthly and keep a week of safety stock and that’s about 22 days, so 60 days is nearly three times what that rhythm needs.
The gap is extra safety stock, bigger orders, slow movers or habit. It might be exactly what you want, or cash you’d rather have back. Either way, you’re choosing it instead of discovering it.
Finished goods at 43 days means a month and a half of sales is already boxed and waiting. Whether that’s healthy depends on how quickly you can remake your best sellers. Work in progress is small here, but it’s real stock: batches that are made but not yet filled and labelled still count.
What is a good inventory turnover ratio?
A good inventory turnover ratio reflects your reorder rhythm and shelf life, which for small-batch manufacturers often means four to twelve turns a year.
That range, one to three months of stock, is a rule of thumb rather than a published standard. Perishable inputs such as food ingredients or botanicals should turn toward the faster end. Stable materials such as fabric, glass jars or hardware can sit toward the slower end without spoiling.
Comparing yourself with an industry average only goes so far. We’d argue your own reordering is a better benchmark: for each material, average stock should be roughly half an order plus your safety stock (for finished goods, read batch for order). Longer or less reliable lead times justify more safety stock.
A low ratio usually points to:
- Over-ordering to hit supplier minimums
- A few slow products dragging the average down
- Short-shelf-life materials bought well before you use them
- Materials left over from products you’ve slowed or stopped making
- Finished goods built ahead of demand
It isn’t always a problem. Long cure times, or packaging you can only buy in big minimums, can reasonably push you below four.
A high ratio isn’t automatically good. If you’re running lean enough to reorder in a panic, pay for rush freight or turn orders away, the ratio looks great while the business pays for it elsewhere.
Find your slow movers: turnover by product
Your overall ratio is an average, and an average can bury a slow product. Look at products one at a time. Start with each product’s sales rate (what people call SKU velocity), then set it against what you’re holding.
The measure is days of cover: units on hand divided by average units sold per day. A product with 300 units on hand selling 5 a day has 60 days of cover. One with 60 units selling 10 a day has 6.
Sort the list by days of cover. The top is where cash is stuck. The bottom is where you’ll stock out first.
How to improve your inventory turnover ratio
If the numbers say you should, these are the levers that move it for a small-batch manufacturer:
- Buy to your usage, not the supplier’s price break. A discount for six months of stock ties up six months of cash. Check the saving is bigger than what that cash could do for you elsewhere.
- Set reorder points from lead time and usage. Buy when you need to, not when the shelf looks empty. Our reorder point formula walks through it.
- Size batches to how fast you sell. A batch that takes four months to sell through is stock before it’s a sale. Production planning and scheduling covers matching production to demand.
- Deal with slow products. Bundle them, discount them or stop making them. Don’t keep re-making them out of habit.
- Get your costs consistent first. COGS and inventory value need to be costed the same way, from the same records, or the ratio can move for reasons that have nothing to do with how fast you sell. An accurate bill of materials keeps both numbers honest.
Turnover is one of several production planning KPIs worth tracking. Together they show whether you’re making money or just staying busy.
Where the numbers come from
The ratio is one division. The hard part is trusting the two numbers that go into it.
If your materials live in one spreadsheet, your batches in another and your sales in a third, getting last quarter’s closing stock value means rebuilding it from all three. That’s a month-end project, and month-end projects get skipped.
Stocksmith keeps your inventory, batches and sales in one set of records. Inventory value and cost of goods sold for any date range become a lookup, so you can run the ratio every quarter and see a drift before it costs you.
Frequently Asked Questions
How do I calculate the inventory turnover ratio?
Divide cost of goods sold by average inventory value for the same period, where average inventory is the opening value plus the closing value, divided by two. For example, $420,000 of COGS over $105,000 of average inventory gives a ratio of 4.0, or about 91 days of stock. Use cost, not revenue, and count the same costs in both numbers. Stocksmith pulls both inputs from the same records for any date range.
What is a good inventory turnover ratio for a small manufacturer?
Four to twelve turns a year is a workable rule of thumb for small-batch manufacturers, meaning stock cycles every one to three months. Perishable inputs should turn faster than stable ones such as fabric or glass, and long cure times can justify less. A better test is whether the average stock of each material is close to half an order plus your safety stock.
What's the difference between inventory velocity and inventory turnover?
They're usually the same thing. Inventory velocity, stock velocity and stock turn all describe cost of goods sold divided by average inventory. SKU velocity or sales velocity is different: it means units sold per day or week for one product. Check how a report defines the term before comparing numbers.
What's the difference between inventory turnover and days of inventory?
Days of inventory is the turnover ratio expressed as time: divide 365 by the annual ratio. A ratio of 4.0 means about 91 days of stock on hand. Turnover is easier to track over time, while days is easier to set against supplier lead times and production cycles, so it's worth watching both.
How do I improve my inventory turnover ratio?
Start with the slowest products and the materials that sit longest before use. Set reorder points from lead time and usage, size batches to how fast you sell, and bundle, discount or retire slow movers. Value COGS and inventory on the same basis too, because mismatched costs make the ratio look precise and mislead you.
Can Stocksmith help me track inventory turnover?
Stocksmith gives you the two numbers the ratio needs. It keeps your materials, batches and sales in one set of records, so inventory value and cost of goods sold for any date range come from one place, with no spreadsheet rebuild. Average the opening and closing values, divide COGS by the result, and you know how fast your stock is turning.
Run the number once, then keep checking
Work out your ratio once with real figures and you’ll know how long your money sits on a shelf before it comes back, which is more than a glance at the stockroom can tell you.
Do it every quarter and the trend becomes an early warning. Start a free 14-day trial and run it on your own numbers.
