Setting WIP Limits in Kanban to Reduce Bottlenecks

Setting WIP limits in kanban: choose, enforce and tune work in progress limits per column so bottlenecks surface early and started work gets finished.

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At a Glance

Overview

Setting WIP limits in kanban means deciding the maximum number of work items allowed in a part of the workflow at one time, then treating that number as a rule the team follows. Kanban work in progress limits are the mechanism that turns a board into a pull system. The Kanban Guide requires that team members "explicitly control the number of work items in a workflow from started to finished" and start new work only when there is a clear signal of capacity (The Kanban Guide). Without that control, a board records work but does not change how it flows. For the wider method, see the Kanban method page.

A limit can apply to a column, a group of columns, a swimlane, a person, a work type or the whole system. Kanban University lists all of these as valid places to limit WIP and describes a limit as a policy that prevents starting new work "when downstream capacity is already utilized and unable to complete the work" (Official Guide to The Kanban Method). The right choice depends on where the team loses time. Per-column limits on the active stages make an easy starting point because they are simple to see and discuss.

Limits do two jobs. First, they reduce the number of things each person is juggling, which cuts the cost of switching between them. Second, they make bottlenecks visible: when a downstream column is full, cards pile up upstream, and the team can see exactly where flow stops. That visibility is how kanban bottleneck reduction starts. The response to a full column is to help finish what is in it, which is why limits change behavior as well as numbers.

The skill is mostly about the conversation around the number. A limit nobody respects does nothing, and a limit set without the team's agreement tends to be quietly ignored. The work here is choosing a sensible starting point, agreeing on what happens when a limit is reached, and tuning the limits from what the board shows over the following weeks.

How It Works

The reasoning behind WIP limits comes from queuing theory. Little's Law, which John Little proved in 1961, states that the average number of items in a queuing system equals their average arrival rate multiplied by the average time each spends in the system (Little, Little's Law at 50). Applied to a stable kanban system, it means that if throughput stays the same, more items in progress means each item takes longer. Capping WIP is the lever the team controls directly.

A limit creates the pull signal. When a column holds fewer items than its limit, someone may pull the next item in. When it is at the limit, nobody starts new work there; instead people help move items out, by reviewing, testing, unblocking or pairing. The Kanban Guide says members "should refrain from selecting more than the number of work items into a given part of the workflow beyond the WIP control."

Where you place limits shapes what they reveal. Per-column limits show which stage is the constraint. A limit across several columns, such as development through testing, lets people shift between those stages while still capping total work. A per-person limit protects individuals who serve several teams. A lane for expedited work often carries a limit of its own, so urgent items do not become a way around the system. Kanban University's guide describes an expedite class of service that may pass even when a limit is exhausted, under agreed rules.

Exceptions must be written down. The Kanban Guide states that "any acceptable exceptions to controlling WIP should be made explicit." A team that allows unlimited exceptions has no limit. A team that allows none may block genuine emergencies. The usual answer is a narrow, visible exception path with its own cap.

Tools vary in how they enforce limits. In Jira, column constraints turn the column header red when the maximum is exceeded but do not change how many items are shown (Atlassian, Configure columns). GitHub Projects highlights a column over its limit but does not stop people or automations from adding cards (GitHub Docs, board layout). In both cases, the limit holds only because the team agrees to honor it.

Limits are hypotheses. After a few weeks you look at how often each column hit its limit, how long items waited upstream, and whether cycle time moved. A limit that is never reached is too loose to change behavior. A limit that is always hit may be marking a real constraint, which is useful to know before loosening it.

Step-by-Step Guide

Step 1: Map the stages and who works in each

List the active columns on your board and the people who usually work items in each stage. Note which stages are waiting states, such as "Ready for review," and which are active work. Record how many items are in each column today. This gives you a baseline and shows where work is already piling up.

Step 2: Choose where to apply limits

Decide whether to limit individual columns, groups of columns, lanes or people. Per-column limits on active stages are the simplest starting point. If people move freely between two stages, consider one limit across both. If an expedite lane exists, give it a small separate limit.

Step 3: Pick starting numbers

Base each limit on the stage's capacity and treat today's count only as the baseline. A reasonable first guess ties the limit to the number of people working in the stage; for example, a review stage staffed by two people might start with a limit of two. If today's count is far above the new limit, plan to let the column drain rather than moving cards backward. Expect the numbers to change.

Step 4: Write the rules for reaching a limit

Before announcing limits, agree on what people do when a column is full: help finish items in that column or downstream, then pull. Write the exception path, who may use it and how many items it allows at once. Decide how blocked items count, and make that rule visible. The Kanban Guide asks that exceptions be explicit, so put them on or beside the board.

Step 5: Apply the limits and brief the team

Show each limit at the top of its column and post the rules next to the board. Walk the team through a few scenarios, such as a full review column when a developer finishes a task. Ask for objections now, because a limit the team does not accept will be bypassed. Agree on a date to review the limits together.

Step 6: Observe flow at the limits

For a few weeks, note each time a column hits its limit and what people did next. Watch for cards piling up in front of a full column, people working around the limits, and items aging in place. A cumulative flow diagram makes these patterns easy to see.

Step 7: Adjust one limit at a time

Change the limit where the evidence is clearest, and change only that one so you can see its effect. Tighten a limit that is never reached. For a column that is always full, look at the stage's capacity and policies before raising its limit, because the full column may be the system's real constraint. Record each change and the reason for it.

Step 8: Review limits in your regular cadence

Make limits a standing item in a retrospective or service delivery review. Check exception use, limit breaches and cycle time trends since the last change. Retire rules nobody needs and write down the ones the team keeps relying on.

Best Practices

• Start slightly tighter than feels comfortable. A small amount of tension shows where work waits, while a loose limit changes nothing about how the team behaves.
• Treat a full column as a signal to swarm. When work cannot move downstream, the most useful thing is usually to help finish what is already there.
• Make exceptions visible and capped. The Kanban Guide requires acceptable exceptions to be explicit, and a capped expedite lane keeps urgent work from swamping the system.
• Limit waiting states as well as active ones. Queues such as "Ready for review" hide a lot of delay, and limiting them exposes it.
• Keep limits where everyone can see them. Kanban University typically shows a limit as a number above the column, and a limit only on a settings page is easy to forget.
• Decide changes from observed flow. Change one limit at a time and watch the effect on cycle time and aging items before changing another.

Common Mistakes

• Setting limits from today's overloaded state: If a column holds a large backlog and you set the limit to match, nothing changes. Set it from the stage's capacity and let the column drain.
• Letting managers bypass limits routinely: Frequent overrides teach the team that limits are optional. Route urgent work through a capped expedite lane with a written policy.
• Counting only some work: Leaving support tickets or side requests off the board makes limits look respected while real WIP stays high. Everything the team works on belongs on the board.
• Raising a limit every time it is hit: A limit that is often reached may be marking the true constraint. Investigate the stage's capacity and policies first.
• Relying on the tool to enforce limits: Tools such as GitHub Projects display limits without blocking cards. Enforcement comes from the team's agreement.

References

• Examples: Worked examples and scenarios
• FAQ: Frequently asked questions
• Parent Method: Kanban

Related Skills

• Designing Kanban Boards
• Creating Kanban Pull Policies
• Measuring Kanban Flow Metrics
• Running Kanban Cadences
• Managing Projects with Kanban
• Comparing Kanban and Scrum
• Choosing Kanban Software

Sources

• The Kanban Guide
• The Official Guide to The Kanban Method (PDF)
• John D. C. Little: Little's Law as Viewed on Its 50th Anniversary
• Atlassian Support: Configure columns
• GitHub Docs: Customizing the board layout

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