Inventory turnover, or turnover rate, measures the number of times inventory is renewed over a given period. It shows how fast goods are sold and then replaced.
For a merchant, this metric helps in particular to spot the products that stay in inventory for a long time, those that sell quickly, and the items whose inventory level deserves adjusting.
But high turnover isn't automatically good, just as low turnover isn't systematically bad. The rate only makes sense when compared with the product, the period and the available inventory level.
How do you calculate the inventory turnover rate?
A commonly used formula divides the cost of goods sold by the average inventory over the same period:
Inventory turnover = cost of goods sold ÷ average inventory
Average inventory can be estimated simply as follows:
Average inventory = (opening inventory + closing inventory) ÷ 2
Let's take an example. Over a year, a store records:
- cost of goods sold: €120,000;
- average inventory: €30,000.
The turnover rate is therefore:
120,000 ÷ 30,000 = 4
The inventory was renewed about 4 times over the year.
This corresponds to an average holding period of about three months, but this equivalence remains an average: it obviously doesn't mean that the entire inventory is replaced exactly every three months.
Can you calculate turnover in units?
Yes.
To analyze a specific item, you can also work in quantities, as long as you keep the same unit in the numerator and the denominator:
Turnover in units = quantity sold over the period ÷ average inventory in units
For example, if 240 units of a product were sold over the year with an average inventory of 40 units:
240 ÷ 40 = 6
The inventory of this item therefore turned over about six times over the period.
The important thing is not to mix units: a sales amount must not be divided by an inventory expressed in number of pieces.
How do you interpret low or high turnover?
High turnover indicates that inventory is renewed frequently. Low turnover means goods stay in inventory longer on average.
But the number alone doesn't let you conclude that a situation is good or bad. Low turnover can be perfectly normal for an expensive item or one that's sold only occasionally. Conversely, very high turnover can become a problem if the inventory level is too low to meet demand.
What is “good” inventory turnover?
There is no universal rate. Turnover depends in particular on:
The sector
A food store, a clothing store and a jeweler don't have the same renewal rhythms.
The product
A high-demand item and a niche item don't turn over at the same pace.
The season
A seasonal item can go through periods of very high turnover followed by several much quieter months.
The business model
Margin, storage cost, supplier lead times or the breadth of the assortment can also change the turnover level you're aiming for.
It is therefore generally more relevant to compare:
- an item with its own history;
- comparable products with each other;
- a category over several periods;
- several comparable stores.
An unusual change is often more informative than a rate considered in isolation.
Low turnover: when should you worry?
Low turnover means a product stays in inventory longer. This can lead to:
- cash tied up;
- space occupied for a long time;
- a risk of depreciation or obsolescence;
- a gradual build-up of inventory.
If the situation persists, low turnover can contribute to overstock or cause dead stock to appear.
But low turnover doesn't automatically mean you should drop the item. Some products sell little while playing an important role in the assortment. Others simply go through a normal slow period. Before acting, you therefore need to understand why turnover is slowing down.
What can cause a drop in turnover?
Several situations can explain why a product turns over more slowly:
- a drop in demand;
- seasonality;
- a change in customer habits;
- a price that has become less competitive;
- a product that is less visible in the store;
- the arrival of a competing item;
- an assortment that has become too broad;
- an initial order that was too large.
Sales analysis complements the turnover metric so you can understand whether the slowdown comes from sales, from the inventory level, or from both.
High turnover: beware of the risk of stockout
High turnover is often seen as positive: the product sells quickly and inventory stays tied up only briefly. But it must be considered alongside available inventory and the restocking lead time.
A product can show excellent turnover while regularly going out of stock. In that case, inventory turns quickly partly because the available quantities are low, and stockouts can prevent some sales from happening.
High turnover therefore doesn't necessarily mean the inventory level is optimal. It should be considered alongside:
- available inventory;
- the pace of sales;
- supplier lead time;
- orders already in progress;
- the risk of stockout.
Turnover and stock coverage: two complementary metrics
Turnover measures how fast inventory is renewed over a period. Stock coverage instead tries to answer a different question: how long can the current inventory cover sales?
A product can therefore have high turnover while showing very low coverage. For example, an item that sells very quickly may have only a few days of inventory left.
Combining turnover and coverage lets you tell apart a high-performing product that is properly supplied from a high-performing product that is about to run short.
How do you improve inventory turnover?
Improving turnover doesn't mean systematically aiming for the highest possible rate. The goal is rather to reduce needlessly tied-up inventory while keeping enough products to meet demand. Depending on the situation, several actions are possible.
Adjust upcoming restocking
When an item slows down for a sustained period, reducing the next quantities ordered avoids building up even more inventory.
Work on merchandising
A product can sometimes sell more slowly simply because it lacks visibility. A change of location or presentation can be tested before lowering its price.
Run a promotional action
A targeted promotion or discount can speed up the sell-through of inventory that has become too large, provided you take the margin into account.
Transfer inventory
In a multi-store network, an item can turn over slowly in one store and quickly in another. A transfer can then make more sense than a discount.
Review the assortment
If an item remains in low demand despite the actions taken, it may be worth reducing its importance in the assortment or stopping its restocking.
Compare families, items, periods and stores
Turnover is most valuable when it is compared.
Between product families, it can reveal that one category is slowing down more than the others. Between similar items, it lets you spot an item that is falling behind the rest of its range. Between periods, it helps tell a one-off slowdown from a lasting trend. Between stores, it can show that the same product performs very differently depending on the store.
This last comparison can in particular reveal inventory transfer opportunities, rather than automatically triggering new restocking or a promotion.
How can you use AI to analyze inventory turnover?
With several hundred or thousands of items, manually monitoring how each rate evolves quickly becomes difficult. An AI agent connected to the store's data can make this analysis easier.
The merchant can, for example, ask:
“Which items have the lowest turnover over the last 90 days?”
Then specify:
“Which ones have slowed down sharply compared with the previous 90 days?”
Or:
“Among these items, which ones still have a lot of inventory?”
The point isn't just to get a ranking. The agent can combine several pieces of available information — turnover, sales, inventory or comparison with a previous period — to bring out the items that truly need attention.
From analysis to decision with Gillia
With Gillia's inventory management, the merchant can start from a question about their items and then dig into the results.
For example:
“Identify the items whose next restocking I should reduce.”
The analysis can then take the available data into account to bring out the items concerned. The decision no longer rests only on an isolated turnover rate: it can be placed in the context of sales and inventory.
To understand the whole cycle, also read our guide on in-store inventory management.
Other inventory-related uses let you, for example, know the value of your inventory or start a cycle count.
Good turnover is therefore not the highest possible turnover: it is turnover consistent with demand, the inventory level and supply constraints.