Days of Inventory Outstanding (DIO)

Days of Inventory Outstanding (DIO) is a financial metric that measures how many days on average a company holds inventory before selling it. This key performance indicator helps businesses understand how efficiently they're managing their stock levels by calculating the average time between purchasing or producing inventory and converting it into sales. A lower DIO generally indicates faster inventory turnover and more efficient operations, while a higher DIO may suggest overstocking or slow-moving products.

Why it matters for e-commerce brands

For Shopify and DTC merchants, DIO directly impacts cash flow and profitability since inventory ties up capital that could be used for marketing, product development, or business growth. E-commerce brands with high DIO risk stockouts of trending items while holding too much slow-moving inventory, leading to markdowns and increased storage costs. Monitoring DIO helps online retailers optimize their purchasing decisions, identify underperforming SKUs, and maintain the right balance between having enough stock to meet demand and avoiding excess inventory.

Example

A Shopify apparel brand has $50,000 in average inventory value and $300,000 in annual cost of goods sold (COGS). To calculate DIO, divide the average inventory by COGS and multiply by 365: ($50,000 / $300,000) × 365 = 61 days. This means the brand holds inventory for an average of 61 days before selling it. If the brand notices their DIO increasing from 61 to 90 days over several months, it signals that inventory is moving slower, potentially due to seasonal changes, overstocking certain products, or declining demand—prompting them to adjust their purchasing strategy or run promotions to clear stagnant stock.

Related terms

• Inventory Turnover Ratio
• Days Sales Outstanding (DSO)
• Cash Conversion Cycle
• Days Payable Outstanding (DPO)
• Average Inventory Value