Inventory Turnover Ratio, DSI & GMROI Efficiency Calculator

Working Capital Management: Inventory Turnover & Velocity

The Inventory Turnover Ratio measures how many times a company sells and replaces its stock over a given period, serving as a primary indicator of supply chain health and liquidity:

• Why Use COGS Instead of Revenue: COGS must be in the numerator because inventory on the balance sheet is valued at cost, not retail sales price. Using sales revenue would artificially inflate the turnover ratio by the profit markup.

• Days Sales of Inventory: Represents the average number of days working capital remains locked up in warehouse physical goods before turning into cash or receivables.

• Gross Margin Return on Inventory Investment (GMROI): Integrates inventory velocity with profit margins. A product with lower turnover (e.g. luxury jewelry at 2x) can be just as profitable as a high-turnover item (grocery at 12x) if its gross margin percentage is substantially higher.

How to Use This Calculator

Enter your Cost of Goods Sold (COGS in ) (e.g. 1,200,000), Beginning Inventory Valuation () (e.g. 180,000), Ending Inventory Valuation () (e.g. 220,000), Total Net Sales / Revenue ( - for GMROI) (e.g. 1,800,000), and Annual Inventory Holding Cost Rate (%) (e.g. 22 (Capital, storage, insurance, shrinkage)). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Inventory Turnover, DSI \& GMROI Financial equations:

Average Inventory = (Beginning Inventory + Ending Inventory) / (2)

Inventory Turnover Ratio (ITR) = (Cost of Goods Sold (COGS)) / (Average Inventory)

Days Sales of Inventory (DSI / DIO) = (Average Inventory) / (COGS) × 365 = (365) / (ITR)

Gross Margin Return on Inventory Investment (GMROI) = (Revenue - COGS) / (Average Inventory) = (Gross Profit) / (Average Inventory)

Annual Carrying Cost = Average Inventory × Holding Cost Rate

Worked Example

For example, analyzing a business with sales revenue of \1,800,000), beginning inventory of \180,000, and ending inventory of \220,000: Average inventory is . The Inventory Turnover Ratio is . Days Sales of Inventory is . The GMROI is \ (\3 gross profit per \1 inventory). At a 22% carrying rate, annual holding cost is .

Understanding Your Result

Optimal inventory management balances holding costs (typically 20–30% of inventory value annually: storage, insurance, obsolescence, capital cost) against ordering costs. EOQ minimizes the total of these two cost types. Safety stock protects against demand variability and lead time variability — the standard formula uses service level z-scores: 95% service level z=1.645, 99% z=2.

• Days inventory outstanding (DIO) benchmark: retail 30–60 days, manufacturing 50–80 days, distribution 20–40 days. Below industry average DIO is generally better.