Most of the advice out there I read on the Kanban method tells you to limit work-in-progress. It seems simple, but in practice, it can be hard to achieve. In this article, I’m going to help you understand how to succeed with limiting work-in-progress and answer the critical question, “How do I determine what WIP limit to use”?
What Are Work-In-Progress Limits
Stop Starting, Start Finishing
Limiting work-in-progress is about starting a limited number of work-items and working on them until they are complete. If you find your team starting new work, before finishing work already started, then work-in-progress limits simply do not exist.
Introducing WIP limits is the quickest way to accelerate delivery while also reducing the stress and overburdening of your teams.
If your team is using a Kanban board and doesn’t use WIP limits, the recommended place to start is by introducing personal WIP limits and then graduating to team WIP limits.
Personal WIP Limits can be applied at the column level if your Kanban board has rows that represent each person’s workload. They can also be applied with Avatars in a more team-oriented Kanban board.
Eventually, members will start talking about trouble keeping their personal WIP limits because of additional work coming into the team. When you start hearing this, it is an excellent time to start encouraging them to implement a team WIP limit.
Team WIP Limits can be applied at the column level or across multiple columns. They can be combined with Personal WIP limits as well.
Identifying the Optimal Work-In-Progress Limit
There is no magic formula for choosing the right WIP limit. The right WIP limit emerges through experimentation. These guidelines can help you increase the chances of successfully adopting optimal WIP limits and reaping the benefits.
What number of work-items are usually in progress every day? For each individual? For the team as a whole? Is there a trend you can identify? Is there some level of consistency?
Have a conversation with your team. Do we have too much work-in-progress for the number of people we have? Does anybody appear to be more overloaded/underloaded than others? The objective of this conversation is to understand the current workload and start talking about taking action to limit work-in-progress.
2- Start High
The primary objective when first using WIP limits is for the WIP limit to survive. For this reason, the team should choose a WIP limit that is just under the average number of work-items observed in progress on a typical day. An aggressive WIP limit can cause havoc early-on and may cause them to reject WIP limits. It’s better to start high, and then encourage them to decrease WIP limits, in the next step gradually.
I am particularly purposeful in getting the team to choose their own WIP limit. One core practice of kanban is to evolve collaboratively and experimentally. If the team doesn’t own the change, it will be unlikely that they will experiment to find their ideal WIP limit. They simply will not improve under these circumstances, and that increases the chances that WIP limits will later be ignored.
3- Decrease Gradually
Imagine you’re driving a car, and there is a problem with the wheels. You may not notice it when driving slowly through your neighbourhood. Hop onto the highway, and as you pick up speed, you feel your car start wobbling. As you move faster and faster, the wobbling gets more violent and harder to control. It’s scary, unsafe, and it makes you uncomfortable. You’re likely going to slow down, inspect why and correct it, before accelerating to that speed again.
WIP limits are a lever that increases delivery speed as well as visibility of problems preventing work-item delivery from further accelerating.
WIP limits are a lever that increases delivery speed as well as visibility of problems preventing work-item delivery from further accelerating. The harder you push this lever, the more your team starts to accelerate, but this tends to expose dysfunctions that prevent teams from accelerating further. Just like a car accelerating with bad wheels, your team can become very uncomfortable under these circumstances, if pushed too aggressively.
Gradually work with your team to decrease their WIP limit, and encourage them to identify issues that they are noticing that are making it challenging to keep their WIP limits.
4- Eliminate Problems Surfaced
Problems that are making it difficult for the team to keep their WIP limits need to be solved so that the team can further decrease work-in-progress and accelerate their delivery. These problems are likely to be in these two categories:
Unexpected Work Being Pushed – These force your team to break personal or team WIP limits, and contribute to more work starting. There is a good chance that some of these are coming from customers as urgent defects, or are coming from internal defects downstream.
Existing Work Being Blocked – Dependencies that cause temptation for the team to pull in more work because they are stuck and have to wait for somebody else on the team or an external team or subject matter expert.
Unfortunately, for both of these, it is easy to say, “if only the team were confident enough to say no to new work, or prioritized unblocking these, then they would be able to maintain their WIP limits and accelerate delivery.” It is neither realistic nor productive to blame the team or ask them to solve these problems on their own. They will need new pragmatic techniques from the Kanban Method that they are unaware of like a replenishment meeting or blocker clustering to help them learn more and alleviate these issues.
5- Decrease Gradually Again
Once the team believes some of the problems identified will no longer occur, it’s time to encourage them to reduce their WIP limit again and discover what else might be preventing them from further accelerating their delivery.
I hope this has helped you think differently about work-in-progress limits. It’s about understanding where the team is, what the workload is like, collaborating to determine a high starting point, and then gradually decreasing the work-in-progress limit while working together to resolve problems. The best-work-in-progress limit is the one that is causing improvement conversation to happen, and you’ll only find that through this gradual and collaborative process.