Inventory turnover ratio: formula, example and tips

The inventory turnover ratio tells you how many times you sell through your average stock in a period, usually a year. A shop that turns its inventory 4 times a year sells roughly a full shelf’s worth of stock every three months. It’s one of the simplest ways to see whether your money is working or sitting in boxes.

This guide covers the formula, how to convert it to days, a worked example in dollars, what a “good” ratio looks like for different small businesses, and practical ways to improve yours.

The inventory turnover ratio formula

The standard formula is:

Inventory turnover = cost of goods sold ÷ average inventory

Two pieces go into it:

• Cost of goods sold (COGS). What the items you sold during the period cost you. Not what you sold them for. If you sold a mug for $18 that cost you $6, that sale adds $6 to COGS.
• Average inventory. The value of your stock at cost, averaged over the period. The simple version is beginning inventory plus ending inventory, divided by 2.

Both numbers need to be at cost. Mixing cost and retail values is the most common mistake, and it makes your turnover look better or worse than it really is. Some people calculate turnover with sales instead of COGS. That’s a rougher version; using COGS keeps both sides of the math in the same units.

You’ll also see this ratio called stock turnover, stock turn, inventory turns or merchandise turnover; they’re the same calculation.

If you’re not sure what counts as inventory, start with what inventory is.

Days of inventory

A turnover of 4 is abstract. Converting it to days makes it concrete. The formula is:

Days of inventory = 365 ÷ inventory turnover

This is roughly how long an average item sits on your shelf before it sells. A turnover of 4 means about 91 days; a turnover of 12 means about 30 days. You’ll also see this called days sales of inventory (DSI) or days inventory outstanding. If you’re measuring a shorter period, use the number of days in that period instead of 365: for a single quarter, use about 91.

A worked example in dollars

Take a small gift shop. At the start of the year, its stock is worth $12,000 at cost. At the end of the year, after a slower fourth quarter than expected, it’s worth $8,000 at cost. Over the year, the items it sold cost $40,000.

1. Average inventory = ($12,000 + $8,000) ÷ 2 = $10,000
2. Inventory turnover = $40,000 ÷ $10,000 = 4
3. Days of inventory = 365 ÷ 4 = about 91 days

So the shop sells through its average stock four times a year, and the typical item sits for about three months.

Turnover by product

The shop-wide number hides a lot. Run the same math for a few individual products or categories and the picture gets more useful:

These categories add up to the shop totals above: $40,000 in COGS and $10,000 in average inventory. Cards and candles move quickly. Ceramics and framed prints tie up nearly 80% of the money in stock while turning much more slowly. That doesn’t mean they’re bad products (they may carry better margins), but it’s where to look first if cash is tight.

When a simple average isn’t enough

If your stock swings a lot during the year, such as a big build-up before the holidays, averaging just the start and end of the year can mislead. Average more points instead: add up your inventory value at the end of each month and divide by 12. The more often you record your stock value, the more accurate the ratio.

What is a good inventory turnover ratio?

There’s no single good number. It depends on what you sell, and the best comparison is usually your own business over time. Some general patterns:

• Food trucks, coffee carts and bakeries turn inventory very fast. Ingredients spoil, so stock is bought in small amounts and used within days. A low turnover here is a warning sign of waste.
• Farmers market produce and prepared food sellers work much the same way: what you bring is meant to sell that day or that week.
• Gift shops, boutiques and general retail sit in the middle. Seasonal and trend-driven items should move within their season; basics can sit longer.
• Craft sellers and makers vary widely. Small, lower-priced items tend to turn faster; one-of-a-kind or high-priced pieces naturally turn slower.
• Jewelry, art, furniture and specialty goods usually turn slowly, balanced by higher margins per sale.

Two things to keep in mind:

• Higher isn’t always better. A very high turnover can mean you’re running out of stock and missing sales. If customers regularly ask for things you’ve sold out of, your stock may be too thin.
• The trend matters most. If your turnover falls from 5 to 3 over two years while sales stay flat, you’re buying more stock than you need, and cash is getting stuck on shelves.

How to improve your inventory turnover

Improving turnover means either selling more of what you hold, or holding less for the same sales. In practice:

1. Find the slow sellers. Run turnover by category or product, or simply sort by what hasn’t sold in 60 or 90 days. That’s where your cash is stuck.
2. Mark down or bundle old stock. A discount now usually beats holding an item for another year. Bundle slow items with best sellers, or put them in a clearance basket at the front of your stall.
3. Reorder smaller and more often. Buying six months of stock to get a bulk discount can cost more in tied-up cash than it saves. Use a reorder point so you restock when you need to, not all at once.
4. Double down on best sellers. Make sure the items that move fastest are always in stock and easy to see. Stockouts on best sellers hurt more than overstock on slow ones.
5. Cut the range, not just the quantity. Ten colors of a scarf where three do all the selling means seven colors of cash on the shelf. Clear SKUs for each variant make this easy to see.
6. Use seasonal timing. Order seasonal goods to arrive just before the season, and plan to clear them before it ends.
7. Rotate stock. Selling older units first keeps items from aging out, which matters most for food, cosmetics and anything with a date. See FIFO inventory.
8. Take pre-orders for big items. Makers can take orders from samples instead of building stock up front.

Keep an eye on margins while you do this. Turnover and margin work together: a product with lower turnover can still be worth carrying if it earns much more per sale. The profit margin calculator helps you check that side.

Where to get the numbers

To calculate turnover you need three things, all at cost:

• your stock value at the start of the period,
• your stock value at the end of the period (or at several points in between),
• the cost of everything you sold during the period.

If you record a cost for each product and your POS system tracks stock, you can pull these from reports instead of counting and adding by hand. Doing a stock count at the same point each period, say the last day of each month, keeps the numbers consistent.

Getting turnover numbers from SleepingFire

SleepingFire doesn’t calculate inventory turnover for you, but it gives you the numbers to do it. Every product has a cost, stock drops with each sale, and the inventory valuation report shows your stock value by category at cost (and at retail), with a CSV export you can drop into a spreadsheet. Sales and profit margin reports show what sold and what it cost you. Take a look at the sales reports and inventory tools.

Frequently asked questions