Retail math · By role
Retail Math for Planners in Apparel
Open-to-buy, stock-to-sales, receipt plan, weeks of supply, BOP/EOP, and plan variance — the core math that drives the merchandise financial plan.
24 formulas for planners
Inventory
Open-to-Buy (OTB)
OTB = Planned Sales + Planned EOP + Planned Markdowns − Planned BOP − Receipts on Order
MarginAlso: Merchandiser
Initial Markup % (IMU)
IMU % = (Retail Price − Cost) ÷ Retail Price × 100
MarginAlso: Merchandiser
Maintained Markup % (MMU)
MMU % = (Net Sales − COGS) ÷ Net Sales × 100
ProductivityAlso: Analytics
Sell-Through Rate
Sell-Through % = Units Sold ÷ Units Received × 100
ProductivityAlso: Executive
Gross Margin Return on Investment (GMROI)
GMROI = Gross Margin $ ÷ Average Inventory at Cost
Inventory
Weeks of Supply (WOS)
WOS = On-Hand Units ÷ Average Weekly Unit Sales
Inventory
Forward Weeks of Supply (FWOS)
FWOS = On-Hand Units ÷ Forecasted Average Weekly Unit Sales
ProductivityAlso: Supply Chain / Ops
Inventory Turns
Turns = COGS ÷ Average Inventory at Cost
MarginAlso: Merchandiser
Markdown %
Markdown % = Markdown $ ÷ Net Sales × 100
InventoryAlso: Designer / Product Dev
Total Line Count (Styles × Colors)
Total SKUs = Styles × Colors × Sizes
InventoryAlso: Designer / Product Dev
Style-Color Depth
Units per Style-Color = Total Buy Units ÷ (Styles × Colors)
MarginAlso: Merchandiser
Allowances %
Allowances % = (Markdowns + Discounts + Chargebacks) ÷ Gross Sales × 100
SalesAlso: Merchandiser
Category Mix %
Category Mix % = Category Sales ÷ Total Sales × 100
Inventory
Stock-to-Sales Ratio (SSR)
SSR = Beginning-of-Period Inventory ÷ Sales for Period
Inventory
Receipt Plan
Receipts = Sales + EOP + Markdowns − BOP
Productivity
Plan vs Actual Variance %
Variance % = (Actual − Plan) ÷ Plan × 100
Inventory
Beginning-of-Period (BOP) Inventory
BOP (Period N) = EOP (Period N−1)
Inventory
End-of-Period (EOP) Inventory
EOP = BOP + Receipts − Sales − Markdowns
InventoryAlso: Buyer
Buy Quantity (Units)
Buy Units = (Sales Forecast Units + EOP Target − BOP) ÷ (1 − Expected Markdown %)
InventoryAlso: Buyer
PO Coverage %
PO Coverage % = Units on Order ÷ Units Needed × 100
InventoryAlso: Buyer
Size Curve Allocation
Units per Size = Total Buy × Size % from Curve
InventoryAlso: Allocator
Fair-Share Allocation
Door Units = Total Allocation × (Door Demand ÷ Chain Demand)
InventoryAlso: Allocator
Replenishment Trigger Point
Trigger = (Lead Time in Weeks × Average Weekly Sales) + Safety Stock
InventoryAlso: Allocator
Safety Stock
Safety Stock = Average Weekly Demand × Safety-Days Coverage ÷ 7
Planner Cheatsheet
Retail Math Cheatsheet for Planners
A role-specific PDF with the formulas planners use day-to-day — equations, worked apparel examples, and the adjacent formulas you work with. Work email only — no sales calls triggered.
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Planners run this math in RetailNorthstar — live.
One connected system from plan to allocation. No more reconciling the spreadsheet, the BI dashboard, and the buy file against each other.