Fill rate measures how much requested demand is fulfilled under a defined rule. A unit fill rate counts units; a line fill rate counts complete order lines; an order fill rate counts complete orders. Always state the denominator and whether “filled” means immediately from stock, on the first shipment or by an agreed date.
Unit, line and order fill rate
Unit fill rate = units fulfilled under the rule / units requested × 100
Line fill rate = complete lines under the rule / lines requested × 100
Order fill rate = complete orders under the rule / orders requested × 100
An illustrative order contains two lines: 50 units of A and 50 of B. The supplier delivers all 50 of A and 40 of B in the first shipment.
- Unit fill rate: 90 / 100 = 90%.
- Complete-line fill rate: 1 / 2 = 50%.
- Complete-order fill rate: 0 / 1 = 0%.
The same delivery legitimately produces three different percentages. If the missing ten arrive later, the eventual fill rate can be 100% while the first-shipment rate remains 90%.
Fill rate is not cycle service level
Cycle service level is the probability that a replenishment cycle has no stockout under the model or measurement rule. Fill rate is the share of demand served. There is no universal conversion such as “95% cycle service means 99% fill rate.” Order size, demand distribution, lead time and shortage size matter.
For example, if 251 of 270 requested units are immediately available, observed unit fill rate is 251 / 270 = 92.96%. That observation does not establish the annual fill rate or the probability of a stockout in future cycles.
Select targets from customer commitments, criticality and the cost of shortages and stock. ABC value alone does not determine an appropriate target: a low-cost component may block an entire service or production run.