What is WIP (Work in Progress) limit?
Answer
Work in Progress (WIP) limits are constraints on the maximum number of items that can be actively in progress simultaneously in each stage of a workflow. They are a core Kanban principle and are also applied in Scrum via Sprint scope. Why WIP limits work: Little's Law states that cycle time = WIP / throughput. Reducing WIP reduces cycle time — items flow faster when the system isn't overloaded. WIP limits: (1) Force collaboration — when a stage is full, upstream workers help unblock items rather than starting new ones; (2) Reveal bottlenecks — if "In Review" hits its limit constantly, it reveals insufficient review capacity; (3) Reduce multitasking — cognitive switching cost from task-switching is eliminated when people focus on fewer items; (4) Improve quality — focused attention produces higher quality work. Setting WIP limits: start with ≥1.5 × team size, then tune based on flow observations. Violating WIP limits should be a conscious team decision, not the norm — it signals a system problem.