Days Sales of Inventory (DSI)

Days Sales of Inventory (DSI) measures how many days, on average, it takes to sell through inventory. Definition, formula, and how to interpret it.

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Days Sales of Inventory (DSI)

Days Sales of Inventory (DSI) measures the average number of days it takes a business to sell through its entire inventory. A lower DSI generally means inventory is moving efficiently; a rising DSI can signal overstocking or slowing demand.

By Tibeau De Grauwe, FounderUpdated September 2026

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What DSI measures

Days Sales of Inventory answers a simple question: at the current rate of sales, how many days would it take to sell through all the inventory currently on hand? It is also called Days Inventory Outstanding (DIO) the two terms mean the same thing.

DSI is closely related to inventory turnover, but expressed in days rather than as a ratio. A lower DSI generally means inventory sells through faster (fewer days of stock on hand); a higher DSI means inventory sits longer before selling.

The DSI formula

DSI = (Average Inventory ÷ Cost of Goods Sold) × Number of Days in the Period. Average inventory is typically the average of beginning and ending inventory value for the period; cost of goods sold (COGS) is the direct cost of the inventory sold during that same period.

For example, a business with $100,000 in average inventory and $600,000 in annual COGS has a DSI of (100,000 ÷ 600,000) × 365 ≈ 61 days on average, it takes about 61 days to sell through inventory on hand.

  • Average inventory: (beginning inventory + ending inventory) ÷ 2
  • COGS: direct cost of inventory sold during the period
  • Period: typically 365 days for an annual DSI figure

Interpreting a rising or falling DSI

A rising DSI over time can signal overstocking, slowing demand, or dead stock accumulating unsold goods sit longer, tying up cash and warehouse space. A falling DSI generally reflects improving sales velocity or tighter inventory management, though an extremely low DSI can also indicate stock levels are too lean, risking stockouts.

"Good" DSI varies significantly by industry: fast-moving grocery and perishables typically run a DSI of days to a couple weeks, while durable goods, specialty retail, or make-to-stock manufacturing can reasonably run a DSI in the months. Compare DSI against your own historical trend and industry peers, not a single universal benchmark.

DSI vs. inventory turnover

Inventory turnover and DSI describe the same underlying efficiency from different angles. Turnover (COGS ÷ Average Inventory) tells you how many times inventory is sold and replaced in a period; DSI (365 ÷ Turnover, or the formula above) tells you the average number of days that takes. Higher turnover corresponds to lower DSI, and vice versa they are mathematically the inverse of each other.

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Frequently asked questions

What is a good DSI (Days Sales of Inventory)?
There is no universal "good" number it varies heavily by industry. Fast-moving goods like groceries typically run a DSI of days to a couple weeks, while durable goods or make-to-stock manufacturing can reasonably run into months. Compare against your own trend and industry peers.
What is the formula for Days Sales of Inventory?
DSI = (Average Inventory ÷ Cost of Goods Sold) × Number of Days in the Period. Average inventory is usually the average of beginning and ending inventory value; the period is commonly 365 days for an annual figure.
Is DSI the same as Days Inventory Outstanding (DIO)?
Yes, DSI and DIO are the same metric under two different names, both measuring the average number of days it takes to sell through current inventory.
What does a rising DSI mean?
A rising DSI over time typically signals overstocking, slowing demand, or accumulating dead stock inventory is taking longer to sell, tying up more cash and warehouse space than before.
How is DSI related to inventory turnover?
They are mathematically the inverse of each other: turnover measures how many times inventory sells through in a period, while DSI measures the average number of days that takes. A higher turnover ratio corresponds to a lower DSI.