Sell-Through & Weeks-of-Supply Calculator
Calculate sell-through, stock coverage, inventory variance, and target-unit gap.
Open toolOne Study decision-preparation calculator
Estimate when stock reaches the point that requires purchasing attention.
Estimate safety stock, reorder point, inventory position, target stock, and order quantity from sales velocity, supplier lead time, current stock, and inbound units.
Calculator
Use recent demand and supplier lead-time records for the same item.
Enter realistic averages and observed highs, not an aspirational service level. The result exposes the buffer implied by those records and how far the current inventory position sits from it.
Reading the result
Compare the inventory position with the lead-time requirement.
The reorder point represents expected demand during average lead time plus the variability buffer produced by the values entered. Inventory position shows whether usable and timely inbound stock currently sits above or below that point.
Before you act
The formula does not see future promotions or supplier disruption.
The estimate does not model demand probability, service-level targets, order calendars, case packs, shelf life, supplier capacity, port delays, promotions, substitutions, or lost-sales history. Use a more detailed inventory model when those factors are material.
FAQ
Questions this tool helps frame.
Why use maximum demand and maximum lead time?
This simple method turns observed variability into a buffer. Use measured highs from a relevant period rather than extreme or hypothetical values.
What counts as inbound inventory?
Include only purchase orders expected to be usable within the lead time being reviewed. Later orders do not protect the same stockout window.
What if the safety-stock result is negative?
The calculator floors it at zero. A negative result usually means the maximum values entered are not actually above the average case.
Is the calculated order quantity a purchase recommendation?
No. It only closes the gap to the target coverage entered. MOQ, cash, shelf life, open-to-buy, and assortment plans still need review.
Working notes
Keep the formula with the assumptions.
- Safety Stock = (Maximum Daily Sales × Maximum Lead Time) - (Average Daily Sales × Average Lead Time); Reorder Point = Lead-Time Demand + Safety StockThe variability method compares an observed high-demand and long-lead-time case with the average case. Inventory position includes usable on-hand units and orders due within the relevant lead time.
- Update the result when the record changesSupplier terms, sales, stock, costs, timing, and channel deductions can change the result materially.
- Continue the operating reviewScaffold, Source4Me
- Check the connected numbersSell-Through & Weeks-of-Supply Calculator, MOQ & Purchase-Order Cash Exposure Calculator, Open-to-Buy Calculator.
- Prepare the non-financial questionsSupplier Readiness Assessment.
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