WIP (Work in Progress) is the set of items that have entered the production process but are not yet finished goods. It includes any material, subassembly, or product unit that is currently being worked on, queued at a workstation, or moving between process steps.
Operationally, WIP is tracked by counting or measuring units at each stage of the process, often with timestamps, locations, and status codes. Systems like MES, ERP, or inventory tools record WIP quantities, routes, and work orders to show where each unit is in the workflow and what operations remain.
WIP levels are typically defined per process step, line, or work center, and may be limited by explicit rules (for example, a maximum number of jobs in a queue). Changes in WIP are driven by production events such as starts, completions, transfers, holds, and scrap, which update the recorded WIP state in real time or near real time.