What is Days Sales of Inventory (DSI)?

DSI measures how many days, on average, a company holds inventory before selling it. A lower number means faster turnover. It is calculated as (Average Inventory / COGS) × Period Days.

It depends on the industry. Grocery retailers often target 7–14 days; manufacturers may carry 30–60 days; specialty retailers can range from 60–120 days. Compare your DSI to industry peers rather than a single universal benchmark.

How is inventory turnover ratio related to DSI?

Inventory turnover = COGS / Average Inventory. DSI = Period Days / Inventory Turnover. They are mathematical inverses: a higher turnover means a lower DSI.

Should I use beginning, ending, or average inventory?

Average inventory ((beginning + ending) / 2) smooths out seasonal swings and gives a more accurate picture. For a rough estimate, ending inventory alone is acceptable.

What does weeks of supply mean?

Weeks of supply is DSI divided by 7. It translates the result into a more intuitive unit — how many weeks of sales you can cover with your current stock.

Inventory Days Calculator

Name: Inventory Days Calculator
Availability: InStock
Author: Nham Vu

Enter your inventory value and COGS to calculate Days Sales of Inventory (DSI), inventory turnover ratio, and weeks of supply.

Inventory Inputs

Average Inventory

(Beginning inventory + Ending inventory) ÷ 2

Cost of Goods Sold (COGS)

Period

Annual (365 days) Quarterly (90 days)

Enter inventory and COGS values to see results.

Summary

Enter your inventory value and COGS to calculate Days Sales of Inventory (DSI), inventory turnover ratio, and weeks of supply.

How it works

Enter your average inventory value (in any currency).
Enter the Cost of Goods Sold (COGS) for the same period.
Select the period length: annual (365 days) or quarterly (90 days).
Click Calculate to see DSI, inventory turnover, and weeks of supply.
Adjust inputs to model different scenarios and compare results.

Use cases

Assess how efficiently a business manages its inventory.
Compare DSI against industry benchmarks to spot inefficiencies.
Model the impact of reducing excess stock on cash flow.
Support quarterly financial reporting and analyst presentations.
Evaluate supplier lead times relative to inventory coverage.
Identify slow-moving product categories in a retail business.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu