Replenishment Trigger Formula
How apparel allocators calculate the replenishment trigger — the on-hand level below which a reorder must fire to avoid stock-out during lead time.
What Replenishment Trigger measures
Replenishment trigger is the inventory level at which a reorder must be placed to cover demand through the replenishment lead time. It is the operational rule for core-and-replenishment apparel categories.
Trigger = (Lead Time in Weeks × Average Weekly Sales) + Safety StockTrigger-based replenishment keeps core basics in stock without over-buying. It applies to styles with stable demand curves — core tees, denim, jackets that run season-to-season.
Worked apparel example
A core tee with 3-week replenishment lead time, 40 units/week average sales, and 30 units of safety stock.
Trigger = 3 × 40 + 30 = 150 units
When on-hand drops to 150, fire the replenishment order. The shipment arrives at roughly week 3, by which point the safety stock buffer has absorbed any above-average demand.
Trigger replenishment at 150 units on hand. Below this level, stock-out risk exceeds service target during lead time.
Failure modes we see
Trigger calculated from plan velocity, not actual. A style slows after Week 4. Trigger is still set to Week 1–3 velocity. Replenishment fires, inventory builds, sell-through drops, markdown follows. The trigger should have decayed with velocity — it did not.
How RetailNorthstar handles triggers
Trigger levels recompute weekly from trailing velocity. Lead-time changes from the supply-chain system update the trigger automatically. For styles flagged as decaying or aged, triggers raise, preventing over-replenishment.
Related formulas
- Safety Stock — the buffer component
- Weeks of Supply — the velocity input
- Door-Level Demand Index — door-specific trigger modifiers
See replenishment triggers that respond to actual velocity — not frozen plan numbers.
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