Average Inventory Calculator
Calculate average inventory, inventory turnover ratio, and days inventory outstanding.
Evaluate how efficiently your business manages stock with industry benchmarks.
How to Calculate Average Inventory
Average Inventory smooths out the natural fluctuation between beginning and ending stock levels to give a representative picture of how much inventory a company typically holds.
Formula:
Average Inventory = (Beginning Inventory + Ending Inventory) ÷ 2
This is the foundation for two critical efficiency metrics:
Inventory Turnover Ratio
Inventory Turnover = Cost of Goods Sold (COGS) ÷ Average Inventory
A higher turnover means you are selling inventory quickly and replenishing often — efficient use of capital. A low turnover suggests overstocking, slow sales, or obsolete products.
Days Inventory Outstanding (DIO)
DIO = 365 ÷ Inventory Turnover
DIO tells you how many days, on average, an item sits in your warehouse before being sold. Lower DIO means faster-moving inventory.
Worked Example
A retailer starts the quarter with $120,000 in inventory and ends with $80,000. Annual COGS is $600,000.
- Average Inventory = ($120,000 + $80,000) ÷ 2 = $100,000
- Inventory Turnover = $600,000 ÷ $100,000 = 6.0×
- DIO = 365 ÷ 6.0 = 60.8 days
Interpretation: This retailer sells through its entire average inventory every ~61 days. For a mid-range retailer, that is reasonable.
Industry Benchmark Turnover Ratios
| Industry | Turnover Ratio | DIO (approx.) |
|---|---|---|
| Grocery / Supermarket | 12–15× | 24–30 days |
| Fast Food / Restaurant | 20–30× | 12–18 days |
| General Retail | 4–6× | 60–90 days |
| Apparel & Fashion | 3–4× | 90–120 days |
| Automotive Dealership | 5–8× | 45–73 days |
| Manufacturing | 3–5× | 73–120 days |
| Electronics | 6–10× | 37–60 days |
| Pharmaceuticals | 3–5× | 73–120 days |
Pro Tips
- Compare your turnover to the same industry — a ratio of 4× is great for manufacturing but poor for a grocery store.
- Turnover that is too high can signal stockouts and lost sales — balance efficiency with availability.
- Use a rolling 12-month COGS and the average of monthly inventory snapshots for the most accurate reading.
- Rising DIO over time often signals slowing demand or purchasing mismatches — a red flag to investigate.
- Average inventory is also a key input for Working Capital analysis and Cash Conversion Cycle calculations.