Inventory Turnover Ratio: Formula and How to Improve It

The warehouse manager reports that stock levels are comfortable, while the finance team looks at the same shelves and sees cash tied up. Inventory turnover is one of the metrics most closely watched in supply chain KPIs, provided it is calculated correctly. This article covers the formula, how to interpret it, and the main levers for improving the ratio.

In short: the inventory turnover ratio is an efficiency ratio measuring how many times inventory is sold and replaced over a period, usually a year. It is calculated by dividing cost of goods sold (COGS) for that period by average inventory over the same period.

The Inventory Turnover Formula and a Worked Example

The numerator of this ratio is cost of goods sold, not sales. Using sales pulls margin into the ratio and makes the figure inaccurate. COGS here means cost of goods sold (cost of goods sold), not cost of goods manufactured. Average inventory is calculated from the opening and closing balances of the period.

Inventory Turnover = Cost of Goods Sold ÷ Average Inventory

Average Inventory = (Opening Inventory + Closing Inventory) ÷ 2

For example, a distributor records annual COGS of Rp 9 billion, opening inventory of Rp 1.2 billion, and closing inventory of Rp 1.8 billion. Average inventory is Rp 1.5 billion, so the ratio is 9 ÷ 1.5 = 6.0 times a year. These figures are illustrative and do not come from any particular company.

The reason the numerator is COGS can be verified. Inventory is carried on the balance sheet at cost: IAS 2 states that inventories are measured at the lower of cost and net realizable value, and the Indonesian equivalent is PSAK 202 “Inventories”. If the denominator is cost-based, the numerator has to be as well.

The 1.43 factor is not an assumption but an arithmetic identity: 1 ÷ (1 − gross margin). The higher the margin, the greater the distortion.

The two inputs come from two different financial statements : COGS from the income statement and the inventory balance from the balance sheet.

What Is a Good Inventory Turnover?

There is no universal number that holds across industries. The valid benchmarks are your own company's trend over time and the average for a comparable sector. The most practical way to make the ratio usable is to convert it into days, because operations teams think in days.

The conversion fits on one line: DSI (days sales of inventory) = 365 ÷ turnover. A ratio of 6.0 times means 365 ÷ 6.0 ≈ 61 days of stock held before it sells.

The “ideal 5–10” figure repeated across various blogs has no primary source. Official data shows that ratio benchmarks depend heavily on sector. The U.S. Census Bureau (MTIS, released 16 July 2026) records seasonally adjusted inventory-to-sales ratios for United States businesses:

This table needs careful reading. What it shows is the inventory-to-sales ratio, not inventory turnover, and the figures are aggregates for the United States. Treat them as reference only, not as targets for a company in Indonesia. Their real value is in showing that on the same metric, in the same country, over the same period, wholesalers (1.15) and manufacturers (1.47) sit roughly 28% apart. If a single number cannot hold across sectors within one country, an ideal ratio across industries certainly cannot.

A high ratio is not automatically a healthy one. If stock runs out and sales fall, average inventory drops faster than COGS, which pushes the ratio up. Inventory turnover therefore has to be read alongside service levels and stockout incidents.

How to Improve Inventory Turnover

The order of actions shapes the result. Fix demand forecast accuracy and stock data quality before adjusting inventory quantities. Deep discounts can lift the ratio in the short term, but they erode margin and leave the root cause untouched. Here are the five main levers, ordered from cause to effect.

1. Demand analysis accuracy. Get the analysis wrong and the stock is wrong from day one; every other lever only cleans up the consequences.
2. Triage slow-moving and dead stock. Separate goods that still hold value, which can be moved through bundling or clearance, from goods worth almost nothing. Stop reordering dead SKUs.
3. Right-size the buffer. An oversized buffer holds the ratio below its potential.
4. Shorten supplier lead times. Stock in transit is still stock and still ties up cash.
5. Ensure stock records are accurate. A ratio calculated from inaccurate data will still produce the wrong answer.

The first and third levers are planning matters. This is where tools such as SAP Integrated Business Planning (SAP IBP) come in. It is designed for multi-echelon inventory optimization and stock positioning based on forecast error and supply uncertainty.

One caution before setting this ratio as a KPI target. The number can be “improved” in damaging ways, such as holding back purchases until stock runs out, which lifts the ratio while sales fall. Pair any ratio target with a service level target.

FAQ (Frequently Asked Questions)

What period is used to calculate inventory turnover?

The standard period is one financial year. If you are using monthly cost of goods sold, multiply by 12 to align with the annual ratio. Comparing periods of different lengths, such as a quarter against a year, leads to misreading performance.

How do you calculate average inventory?

For businesses with stable stock, add opening and closing inventory and divide by two. For seasonal businesses, a two-point average can mislead because it ignores swings mid-period. The common practice among analysts is a 13-point average: twelve month-end balances plus the opening balance for the year.

How does inventory turnover relate to cash flow?

Days of inventory is the first component of the cash cycle. In ASCM's SCOR model, cash-to-cash cycle time is calculated as days of inventory plus days of receivables minus days of payables. Shortening days of inventory directly shortens the gap between cash going out for stock and cash coming back from customers.

Conclusion

The strength of this ratio depends on the accuracy behind it: COGS as the numerator, average inventory as the denominator, interpretation in days, and pairing with service levels. Differences of opinion between the warehouse and finance are settled by accurate data, not by a high number. As an SAP Platinum Partner through United VARs, Soltius supports distribution, manufacturing, and retail companies in implementing SAP to calculate and monitor this ratio.

To discuss inventory planning and SAP Integrated Business Planning at your company, visit soltius.co.id.