Why this matters

Inventory on hand alone does not tell you whether you have too much or too little stock. A useful first step is comparing inventory with recent sales pace.

Calculate units sold per day

Historical velocity = units sold during your selected window ÷ days in that window. If 90 units sold in 30 days, velocity is 3 units/day.

Estimate days of supply

Days of supply = ending inventory ÷ average daily sales. If 45 units remain and velocity is 3/day, you have an illustrative 15 days of coverage at that pace.

Handle zero sales honestly

If daily sales are zero, the estimate is undefined. Do not report “infinite days” as a meaningful demand forecast; label it insufficient sales history and investigate.

Choose the right lookback period

Short windows respond quickly to change but can be volatile. Longer windows smooth noise but can miss recent shifts. Compare periods when seasonality or promotions matter.

Treat estimates as signals

Supplier lead times, inventory by location, incoming orders and unavailable stock influence what to do next. The arithmetic does not replace inventory planning judgment.

Example with numbers

Illustrative calculation: 90 units sold in 30 days yields 3 units/day. With 45 remaining, that implies 15 days of supply at the recent pace.

All example products and numbers on this page are illustrative.

Related inventory guidance

Shopify also documents its inventory remaining report, which uses historical sales to estimate remaining coverage.

Explore related topics:

How InventoryPulse can help

InventoryPulse combines Shopify sales and inventory data to help merchants review product and variant performance, recent selling pace, sell-through and inventory recommendations. Ask InventoryPulse can answer supported questions using available store evidence, with limitations where evidence is insufficient. InventoryPulse does not make guaranteed sales predictions or purchasing decisions.

Explore InventoryPulse on Shopify