FiscalInsights

Inventory Turnover Ratio

Calculate how quickly inventory sells and optimal stock levels.

Formula

Inventory Turnover = Cost of Goods Sold / Average Inventory
Days Sales of Inventory (DSI) = 365 / Inventory Turnover
Average Inventory = (Beginning Inventory + Ending Inventory) / 2

How to Calculate

Inventory turnover measures how many times you sell and replace your inventory in a given period. Divide your cost of goods sold (COGS) for the period by your average inventory value. Use COGS rather than revenue because inventory is recorded at cost.

Average inventory smooths out seasonal fluctuations. Add the beginning and ending inventory values for the period and divide by two. For more accuracy, average monthly ending inventory values over the year.

Convert the turnover ratio to days by dividing 365 by the turnover ratio. This gives you Days Sales of Inventory (DSI)—the average number of days it takes to sell through your inventory. Lower DSI means faster turnover and typically healthier cash flow, though excessively low DSI might indicate stockouts and missed sales opportunities.

Worked Example

A retail store has:
Annual COGS: $480,000
Beginning inventory: $75,000
Ending inventory: $85,000
Average Inventory: ($75,000 + $85,000) / 2 = $80,000
Inventory Turnover: $480,000 / $80,000 = 6.0 times per year
Days Sales of Inventory: 365 / 6.0 = 60.8 days

This store sells through its entire inventory about every 61 days, or 6 times per year. If the industry average is 8 turns, this store may be overstocked or carrying slow-moving products.

Why It Matters

Inventory is cash sitting on shelves. A slow turnover ratio means capital is tied up in unsold products, increasing storage costs, obsolescence risk, and insurance expenses. A healthy turnover ratio means efficient operations, strong demand, and better cash flow. Monitoring this metric helps you optimize purchasing, identify slow-moving products, and reduce carrying costs.

Practical Tips

  • ✓Benchmark your turnover against industry averages—a grocery store turns 14+ times/year while a furniture store might turn 4–6 times.
  • ✓Identify and discount slow-moving inventory before it becomes obsolete—it is better to sell at a discount than not at all.
  • ✓Use demand forecasting to align purchasing with actual sales patterns and reduce excess inventory.
  • ✓Calculate turnover by product category to identify which items need attention rather than relying on aggregate numbers.

Frequently Asked Questions

What is a good inventory turnover ratio?
It varies dramatically by industry. Grocery stores average 14–20 turns per year. Apparel retailers average 4–6. Auto dealers average 6–8. Generally, higher turnover indicates efficiency, but extremely high turnover might mean you are understocked and losing sales due to stockouts.
Why use COGS instead of revenue for this calculation?
Inventory is valued at cost on the balance sheet, so using COGS provides an apples-to-apples comparison. Using revenue would inflate the ratio because revenue includes your markup. Some analysts do use revenue, but the COGS-based calculation is the standard financial metric.
How does inventory turnover affect cash flow?
Faster turnover means you convert inventory to cash more quickly, improving working capital. If you turn inventory 12 times/year (monthly), cash is tied up for about 30 days. At 4 turns/year (quarterly), cash is locked up for 90 days. Faster turns reduce the amount of capital needed to operate.

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