Stockout Rate
Is stockout rate the same as fill rate?
No. Stockout rate measures unavailability or unmet demand; fill rate measures the proportion of demand fulfilled from stock. They are related but not identical and can be calculated on different bases such as orders, units, SKU-days, or time.
Which formulation is best for manufacturing?
For shop-floor control, time-based or demand-weighted stockout rate is usually more informative than a simple count of stockout events because it captures duration and demand impact, which are the drivers of downtime and lost throughput.
What operational signals usually drive a high stockout rate?
Late receipts, inaccurate on-hand quantities, poor min/max settings, lead-time variability, excessive batch sizing, and weak line-side replenishment discipline are common root causes in manufacturing and warehousing environments.
Stockout rate is the percentage or frequency with which a required item is unavailable because inventory has reached zero or cannot meet demand. It measures lost sales or unmet demand exposure, not merely empty shelf time. Common variants include time-based, demand-weighted, and SKU-day calculations, often expressed as unfulfilled orders divided by total demand.
On a shop floor, stockout rate monitors whether parts, WIP pull items, or raw materials are available when a work order is released. A stockout can stop an operation, force resequencing, or create expediting and substitution activity. In warehousing, it quantifies how often a pick face, reserve location, or replenishment bin is empty when a pick or sales order is needed, affecting order fill performance and service level. In raw material tracking, it identifies the share of demand events, SKU-days, or open hours where material was unavailable despite demand, helping determine whether the issue is forecasting error, late receiving, incorrect on-hand balances, or replenishment lead-time mismatch. Common calculation variants include time-based, demand-weighted, and SKU-day rates; a simpler operational formulation is unfulfilled orders or stockout events divided by total orders or demand events, multiplied by 100. The denominator choice determines whether the metric exposes downtime, lost throughput, or customer service impact.
Phantom inventory stockouts: System on-hand shows stock, but the bin is empty because of mispicks, unposted scrap, cycle count errors, or delayed consumption postings. The stockout emerges only when the line or picker arrives, forcing emergency replenishment and expediting.
Replenishment lag at point of use: Material exists in reserve storage but is absent from the line-side supermarket or pick face when needed. Timing, transport delay, or poor kanban sizing causes the shortage, not total enterprise stock deficiency.
Demand spike mismatch: Forecasts, reorder points, or safety stock are set below actual variability, so a surge or schedule change consumes available stock before replenishment arrives. That raises stockout rate and triggers expediting, substitutions, and production stoppages.