The formula
How to calculate inventory turnover
Inventory turnover counts how many times a business sells and replaces its stock in a year. It measures how hard the money tied up in inventory is working.
Use cost of goods sold rather than revenue. Inventory is carried at cost, so dividing revenue by it mixes two different bases and overstates the turnover by the whole gross margin.
What to enter:
- Cost of goods sold
- Average inventory — opening plus closing stock, divided by two
The result updates on every keystroke. The URL updates too, which makes the filled-in version easy to bookmark or send to someone else.
The order the fields are filled in makes no difference to the result — the calculator recomputes the whole formula from whatever is currently in every field, not step by step. That means it is safe to adjust one number, watch the result change, and adjust it back, without worrying about resetting anything first.
Why inventory turnover matters
Most people who look up a inventory turnover calculation already have a specific number in mind — a quote, an offer, a target — and want to check it rather than learn the theory behind it. This page is built for that: enter your own figures, see the result immediately, and change any field to see how the answer moves without redoing the arithmetic from scratch each time.
It is also useful as a sense check before signing anything. A quote, an offer letter or a spreadsheet from someone else can contain an error, an optimistic assumption, or simply a different convention for rounding — running the same inputs through an independent calculator is a quick way to confirm a number before relying on it.
This kind of calculation rarely stands entirely alone. A inventory turnover figure usually feeds into a wider decision — how it compares with a competing offer, whether it fits inside a monthly budget, what it does to a longer-term plan — and the value of having it as an exact number rather than a rough guess is that those follow-on comparisons stop being guesswork too. Once one figure in a decision is precise, it is worth making the effort to get the others precise as well, rather than mixing an exact calculation with several estimates and treating the result as equally reliable.
In practice, most people arrive at a page like this one having already tried a version of the calculation by hand or in a spreadsheet, and use the calculator here to confirm it rather than replace it. That is a reasonable way to use it — the two should agree to the last decimal place if the same inputs and the same formula are used, and if they do not, the formula shown above is the one to check your own working against first.
Worked example
Here is the calculation with the starting values:
- Cost of goods sold: 1,450,000
- Average inventory: 205,000
That gives:
- Inventory turnover: 7.07 × per year
- Days inventory outstanding: 51.6 days
- Weeks of stock held: 7.35 weeks
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
Higher turnover means less capital tied up and less obsolescence risk. Grocery runs 15–25 times a year, general retail 4–8, heavy machinery 2–3. Falling turnover is an early warning that stock is not selling.
Where this goes wrong. Chasing turnover too hard. Very high figures can mean understocking, which shows up later as lost sales and disappointed customers — costs that never appear on the inventory line.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
It is entirely sector-specific. Compare against direct competitors and against your own history; a ratio that is stable or improving matters more than the absolute level.
Average, where you have both figures. Closing inventory alone distorts the ratio for seasonal businesses, which deliberately hold very different stock levels at different points in the year.
It returns inventory turnover. With 1,450,000 cost of goods sold and 205,000 average inventory, that comes to 7.07 × per year. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.