Glossary

Fill rate

The share of customer demand fulfilled immediately from available stock, without delay, backorder, or substitution.

Fill rate is the percentage of demand fulfilled immediately from available stock, without delay, backorder, or substitution. It comes in several variants that can produce quite different numbers for the same underlying performance: unit fill rate (units shipped over units ordered), order fill rate (orders shipped complete over total orders), and line fill rate (order lines filled complete over total lines) — so it matters which version is being reported.

The general formula is fill rate = quantity shipped complete and on time / quantity demanded, expressed as a percentage. It differs from on-time in full, which also folds delivery timing into the measure rather than looking only at whether stock was available.

Retailers and manufacturers use fill rate to set safety stock levels and to negotiate service-level agreements with customers or suppliers. A high fill rate achieved only by carrying excessive inventory can mask weak demand forecasting, so it's usually read alongside inventory efficiency measures rather than as a standalone success metric.

Last reviewed September 22, 2026

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Related terms

On-time in full (OTIF) The share of customer orders delivered both on the promised date and complete, with nothing missing or short. Inventory turnover How many times a company sells and replaces its inventory over a given period, usually a year. Safety stock Extra inventory held beyond expected demand to absorb variability in demand or supply lead time without running out. Demand forecasting Estimating future customer demand for a product so inventory, production and staffing can be planned ahead. Supply chain visibility The ability to track goods, orders, and inventory across every stage of a supply chain, often close to real time.