What is inventory turnover ratio?
Inventory turnover is cost of goods sold divided by average inventory. It tells you how many times the stock on the shelves sells and is replaced in a year. A ratio of 4.00 means the whole stock turns over four times a year — about every 91.25 days.
A higher ratio is usually better: cash comes back faster, less money sits on shelves, and less stock goes stale or out of fashion — but too high can mean empty shelves and lost sales, because there is nothing left to sell. Try the numbers on the inventory turnover ratio calculator and it does the dividing for you.
The inventory turnover ratio formula
The formula is inventory turnover ratio = cost of goods sold ÷ average inventory. The cost of goods sold is what the goods that actually sold cost to buy or make — not what sits on the shelves, and not the sales price. The average inventory is the stock held across the year — opening inventory plus closing inventory, divided by two — because a single end-of-year snapshot can be flattered by a clearance sale or a stock-up.
Step 1: work out the cost of goods sold
Start with what the goods that actually sold cost to buy or make. The cost of goods sold is the purchase cost of the stock that left the shelves — not the sales price, and not the cost of the stock still sitting there. Here is the worked example: cost of goods sold of $800,000. That is what the goods sold in the year cost the business, before a dollar of rent, marketing or wages.
Step 2: work out the average inventory
Take the stock held across the year. The average inventory is opening inventory plus closing inventory, divided by two — because a single end-of-year snapshot can be flattered by a clearance sale or a stock-up. Here is the worked example: opening inventory of $150,000 and closing inventory of $250,000 give an average inventory of $200,000. That is the stock the business held, on average, through the year.
Step 3: divide the cost of goods sold by the average inventory
Divide the cost of goods sold by the average inventory. Here is the worked example: $800,000 ÷ $200,000 = 4.00 times. So the inventory turnover ratio is 4.00 — the whole stock sells and is replaced four times a year. The days inventory outstanding is 365 ÷ 4.00 = 91.25 days — on average, a unit sits on the shelf for 91.25 days before it sells. The inventory turnover ratio calculator runs the division for you.
Three worked examples
Example one — the headline numbers. A business has cost of goods sold of $800,000 and average inventory of $200,000. The ratio is $800,000 ÷ $200,000 = 4.00 times, and the days are 365 ÷ 4.00 = 91.25 days.
Example two — working to a target. A business wants a ratio of 6.00 and it holds $200,000 of average inventory. The cost of goods sold it needs is 6.00 × $200,000 = $1,200,000. The other way round, a business with $800,000 of cost of goods sold can hold at most $800,000 ÷ 6.00 = $133,333.33 of average inventory and still keep a 6.00 ratio. The inventory turnover ratio calculator runs the target check for you.
One reverse to check your answer
Work the numbers backwards. A business wants a ratio of 6.00, and it holds $200,000 of average inventory. The smallest cost of goods sold that reaches the target is $1,200,000. A dollar less, and the ratio falls short of the 6.00 target — at $1,199,999 the ratio is 5.999995, which displays as 6.00 but is below the target. The inventory turnover ratio calculator runs the reverses for you.
What a 4.00 ratio means
A 4.00 ratio means the whole stock sells and is replaced four times a year — about every 91.25 days. At that pace the business turns its shelves over every three months, so cash comes back fast and little money sits on shelves. Compare the ratio within one industry, not across them — a grocer at 12.00 and a jeweller at 1.50 can both be healthy, because their stock turns at different speeds by design.
High ratio vs low ratio
Typical ratios run 4–6 for general retail, 12 or higher for groceries, and lower for luxury goods and furniture. A high ratio means the stock moves fast — cash comes back faster, less money sits on shelves, and less stock goes stale or out of fashion. A low ratio means cash is trapped in stock — the classic overstock warning is a ratio that falls year after year while inventory rises.
Why the ratio is read year over year
A ratio that falls year after year while inventory rises is the classic early warning — the business is buying stock faster than it sells it. Read the ratio year over year, and the pattern tells you whether the business is turning its stock faster or letting it pile up.
What a negative ratio means
A negative ratio means the cost of goods sold printed negative. Here is the worked example: cost of goods sold of −$50,000 and average inventory of $200,000 give a ratio of −0.25. A negative cost of goods sold means returns and adjustments exceeded purchases — a data problem, not a real turnover. The calculator shows the negative figure with a note, never hides it and never shows “—” for it.
What if the average inventory is zero?
At $0 of average inventory the ratio is undefined — there is no stock to turn over, so there is nothing to divide by. The calculator shows the ratio as undefined with that note, never a crash and never a made-up number. At $0 of cost of goods sold the ratio is 0.00 times and the days figure is undefined — nothing sold, so there is no days figure.
The mistakes to avoid
Four mistakes catch almost everyone. First, mixing up inventory turnover and inventory to sales: inventory to sales divides sales by inventory, which uses the selling price, so it overstates turnover whenever margins are high — cost of goods sold is the honest numerator. Read the guide to inventory to sales for the other side of the same stock. Second, mixing up turnover and gross profit margin: margin measures how much profit each sale keeps, turnover measures how fast the stock moves — a business needs both, and a high margin with a low turnover is a slow business. Third, using ending inventory instead of the average: a single end-of-year snapshot can be flattered by a clearance sale or a stock-up. Fourth, reading one year as the whole story: a ratio that falls year after year while inventory rises is the classic early warning, so read the ratio year over year. The days inventory outstanding calculator, the operations ratios calculator and the gross profit margin calculator cover the rest of the same accounts.