Days of Inventory Calculator
Days of inventory (also called days sales of inventory, DSI) estimates how many days your current stock will last at your current cost of sales. Divide average inventory by COGS and multiply by the days in the period. Lower generally means leaner, faster-moving stock. Enter your numbers below to get your DSI instantly.
Lower is generally better — less cash tied up in stock.
The formula
Worked example
With $40,000 of average inventory at cost, $250,000 of annual COGS and a 365-day period: DSI = (40,000 ÷ 250,000) × 365 ≈ 58 days. Your stock lasts about two months — an implied turnover of about 6.3× a year.
Stop calculating by hand
Logistified computes this across your whole Shopify catalog automatically — from live sales data — and turns it into reorder alerts and purchase orders.
Frequently asked
What is days of inventory?
Days of inventory — also called days sales of inventory (DSI) or days inventory outstanding — estimates how many days it takes to sell through your average stock. It's average inventory divided by COGS, multiplied by the number of days in the period. It translates an abstract turnover ratio into a tangible number of days.
Is a lower days-of-inventory number better?
Generally yes — fewer days means leaner, faster-moving inventory and less cash tied up. But too low can mean you're risking stock-outs and lost sales. The right level balances availability and service against carrying cost, and varies by category and lead time.
How is days of inventory related to inventory turnover?
They're two views of the same thing. Days of inventory = days in period ÷ inventory turnover. If you turn inventory 6 times a year, that's about 365 ÷ 6 ≈ 61 days of inventory. Use turnover for a ratio and days for an intuitive timeframe.