Sell-Through Rate
Also known as: STR, Inventory Sell-Through
Sell-through rate is the share of available inventory sold over a period — units sold divided by units available (sold + on hand) — a key gauge of how fast stock is moving.
Sell-through rate (STR) measures how quickly inventory converts to sales over a window. A common formula is Sell-Through Rate = Units Sold / (Units Sold + Units On Hand) × 100 for the period, expressed as a percentage; a higher rate means stock is turning fast and a lower rate signals overstock or weak demand.
Amazon uses a related metric in the Inventory Performance Index (IPI): the FBA sell-through ratio (units shipped over the trailing window divided by average inventory) is one of IPI's core components. Low sell-through drives down IPI, which can trigger storage limits and aged-inventory surcharges, so it has consequences beyond a vanity number.
Sell-through is the heartbeat of restock and liquidation decisions: high STR plus low days-of-cover means reorder now; low STR plus aging inventory means consider a price drop, ads, or liquidation before the aged-inventory surcharge erodes the position.
A SKU sold 300 units last month and has 200 units on hand. Sell-through rate = 300 / (300 + 200) = 60% — healthy turnover that supports reordering rather than liquidating.