Inventory Turnover

Inventory turnover (also called stock turn, inventory turns, or the inventory turn ratio) measures how many times a company sells through and replaces its inventory over a specific period — typically a year. It is one of the most fundamental metrics in supply chain and financial management, indicating how efficiently a business manages its inventory relative to its sales volume.

The Formula

Inventory Turnover = Cost of Goods Sold (COGS) ÷ Average Inventory

Where Average Inventory = (Beginning Inventory + Ending Inventory) ÷ 2

A related metric, Days Sales of Inventory (DSI), converts the ratio into days:

DSI = 365 ÷ Inventory Turnover

DSI tells you how many days of sales your current inventory represents. A DSI of 30 means you have a 30-day supply of inventory on hand.

Interpreting Inventory Turns

Higher inventory turnover generally indicates:

• Efficient inventory management
• Strong sales relative to inventory investment
• Lean operations with minimal excess stock
• Lower holding costs and working capital requirements

Lower inventory turnover indicates:

• Excess inventory or slow-moving stock
• Demand forecasting issues
• Potential for obsolescence, especially in fast-changing categories (electronics, fashion)
• Higher carrying costs consuming margin

However, context matters enormously. An extremely high turnover might indicate insufficient safety stock, leading to frequent stockouts. The optimal turnover rate varies significantly by industry.

Industry Benchmarks

Inventory turnover benchmarks vary dramatically by sector:

Amazon's retail operations achieve industry-leading turns of 10–12×, representing one of the key efficiency advantages of its demand-driven, technology-managed inventory model.

What Drives Inventory Turnover

Sales velocity: Higher-demand products turn faster. ABC inventory analysis typically shows that A-items (top 20% of SKUs) represent 80% of turns.

Lead times: Shorter replenishment lead times allow lower safety stock and faster turns without increasing stockout risk.

Demand forecasting accuracy: Better forecasts mean less safety stock needed to maintain service levels, improving turns.

Product lifecycle: Fashion, electronics, and perishable goods have inherently faster ideal turns than durable goods; holding them too long destroys value through obsolescence.

Promotions and markdowns: Clearance pricing accelerates turns but reduces margin — a deliberate tradeoff to free working capital and shelf space.