Weeks of Supply
A metric that estimates how many weeks current inventory will last at the current rate of sales, helping buyers plan replenishment timing.
Weeks of Supply is a metric that estimates how many weeks current inventory will last at the current rate of sales, helping buyers plan replenishment timing. It's calculated by dividing on-hand inventory units by average weekly sales units. This forward-looking measure enables businesses to assess whether they have too much stock (risk of obsolescence) or too little (risk of stockouts).
Why it matters for e-commerce brands
For Shopify and DTC merchants, Weeks of Supply helps prevent costly stockouts that directly impact revenue and customer satisfaction. Unlike traditional retail where customers might accept backorders, e-commerce shoppers typically abandon their cart and purchase from competitors when items are unavailable. Maintaining optimal Weeks of Supply ensures you can fulfill orders consistently while avoiding excess inventory that ties up cash flow and incurs storage fees.
Example
A skincare brand on Shopify has 800 units of their bestselling moisturizer in their warehouse. Based on the past four weeks, they're selling an average of 100 units per week. Their Weeks of Supply calculation is 800 ÷ 100 = 8 weeks. If their supplier lead time is 6 weeks, this indicates they should reorder soon to avoid a stockout. However, if they're planning a promotional campaign that typically doubles sales velocity, their actual Weeks of Supply would drop to 4 weeks, signaling an urgent need to increase their order quantity or expedite shipping.
Related terms
- Days of Inventory
- Inventory Turnover
- Lead Time
- Reorder Point
- Safety Stock
Put Weeks of Supply knowledge into practice
Forthsuite's tools are built around exactly these concepts — giving Shopify merchants the data and automation to manage their supply chain with confidence.