Amazon FBA Glossary

The inventory terms that actually move money on Amazon, defined in plain English. Each one explains why it matters for a private-label seller and how it ties into your restock decisions.

• IPI (Inventory Performance Index)

  The 0 to 1,000 score Amazon uses to decide how much FBA storage you get.

• Sell-Through Rate

  Units sold divided by average units on hand. The core efficiency number.

• Days of Supply

  How many days your stock lasts at current sales velocity.

• Reorder Point

  Demand during lead time plus safety stock. The trigger to reorder.

• Safety Stock

  The buffer that absorbs demand spikes and late shipments.

• Lead Time

  Order to sellable: production plus freight plus FBA check-in.

• FNSKU (Fulfillment Network Stock Keeping Unit)

  The Amazon barcode that ties a physical unit to your account.

• Aged Inventory Surcharge

  Escalating FBA fees on inventory that sits too long.

• Low-Inventory-Level Fee

  An FBA fee for running chronically thin on fast-moving SKUs.

• Restock Limits

  Amazon's cap on how much inventory you can send into FBA.

• FBA Inbound Placement Service Fee

  Per-unit FBA fee for shipping inventory into Amazon's network. Cheaper or free when you split the shipment as Amazon recommends.