Fixed Order Interval

Fixed Order Interval (FOI) is a periodic review inventory control system in which inventory is checked and replenishment orders are placed at predetermined time intervals; the order quantity varies because it is calculated to raise stock back to a target level rather than to a fixed lot size. In practice, planners review stock on a schedule such as weekly or monthly and order enough to cover demand during the review period plus lead time.

On a manufacturing shop floor, FOI shows up when line-side materials are consumed continuously but replenishment is batched into calendar rhythm. A material handler counts or scans stock at the review point, then issues a variable order to bring inventory back to a target level. That target covers expected usage over the protection interval—review period plus supplier lead time—with safety stock. Weekly kanban cart fills, monthly raw-material buys, and cyclic MRO replenishment all follow this pattern. In warehousing, FOI suits stable-demand items, supplier consolidation, or limited receiving capacity because purchases and inbound receipts are grouped into planned windows rather than triggered by every consumption event. The system reduces continuous reordering and smooths dock and putaway workload, but it demands accurate inventory visibility at review time; if counts, barcode scans, or scrap postings are wrong, the target-level calculation is off and shortages can appear before the next review.