Weeks of supply calculator
Weeks of supply (also called weeks of cover) is how many weeks your current inventory will last at the current sales rate. It is calculated as current inventory ÷ average weekly sales.
Add incoming receipts to see cover including stock already on order.
- Definition — Weeks of supply
- Weeks of supply (also called weeks of cover) is a forward-looking view of how long current stock lasts at the current rate of sale. Low cover signals stockout risk before replenishment lands; high cover signals overstock and building markdown pressure. It is the mirror image of inventory turnover — more turns means fewer weeks of supply on hand.
- Weeks of supply = current inventory ÷ average weekly sales
- Used by: Merchandise planners, allocators, replenishment and trading teams
- Related: Weeks of cover, inventory turnover, WSSI, open-to-buy, sell-through
Merchandise planners, allocators, and replenishment teams watching whether stock will last across SKUs, channels, and locations.
Use it in-season to flag stockout or overstock risk early, and to translate cover into an OTB, replenishment, or allocation action.
Spreadsheets are useful when the process is small and controlled. They become risky when multiple teams need the same version of the plan, when assumptions change frequently, or when decisions must flow into POs, production, and allocation.
- Compare weeks of supply to your replenishment lead time — cover should comfortably exceed it.
- Refresh the average weekly sales figure as demand trends shift.
- Use the receipts view to confirm on-order stock closes any cover gap in time.
- Translate low or high cover into an OTB, replenishment, or allocation action.
See cover in the weekly trading view with the WSSI calculator, manage intake budget with the open-to-buy calculator, or compare with the inventory turnover calculator.
Frequently asked questions
- What is weeks of supply?
- Weeks of supply (WOS) is how many weeks your current inventory will last at the current rate of sale. It is calculated as current inventory ÷ average weekly sales, so 800 units selling 100 a week is 8 weeks of supply.
- What is weeks of cover?
- Weeks of cover means the same thing as weeks of supply — how many weeks of demand your stock covers. The two terms are used interchangeably; "cover" is more common in UK and European retail planning.
- How many weeks of supply is healthy?
- It depends on lead time, category, and how often you replenish. The target should comfortably exceed your replenishment lead time so you do not sell out before new stock lands, without holding so much that capital is tied up. Fast-replenishing basics run leaner than long-lead seasonal apparel.
- How is weeks of supply different from inventory turnover?
- They are two views of the same thing. Weeks of supply is forward-looking — how long current stock lasts at the current sales rate. Inventory turnover is backward-looking — how many times you sold through average inventory over a past period. Roughly, more turns means fewer weeks of supply on hand.
Your calculator result is one number. RetailNorthstar keeps the whole plan connected — line plan, OTB, assortment, buy, POs, and production.
- Weeks of supply is how many weeks current inventory will last at the current or forecast sales rate.
- Weeks of supply = current inventory ÷ average weekly sales; adding receipts shows cover once on-order stock lands.
- Low cover signals stockout risk; high cover signals overstock and markdown pressure.
- Cover should comfortably exceed replenishment lead time, and it is the forward-looking mirror of inventory turnover.
- RetailNorthstar connects weeks of supply to WSSI, OTB, replenishment, allocation, and purchase order decisions.