Why We Need WIP Limits
Stop Starting, Start Finishing
The goal of any Lean/Kanban practice is to maximize value for the customer while eliminating waste. In Lean thinking, waste is defined as anything that does not add value to the customer. WIP limits (work-in-process limits) are fixed constraints, typically implemented on Kanban boards, that help teams actively eliminate waste from their processes. WIP limits enable teams to optimize their workflows for value delivery.
The main idea behind WIP limits can be explained by this simple phrase: Stop starting, start finishing. WIP limits encourage us to finish work that’s already in process before introducing more work into the system. Because the more work teams try to juggle at once, the harder it is for them to take work to the finish line.
In this post, you’ll learn how WIP limits can help teams identify, then reduce or eliminate the most common sources of process waste, so they can more effectively deliver value to their customers.
Defining WIP Limits
WIP limits are constraints on how many work items (cards) are actively being worked on at any given time. They can be implemented at the individual, team, and even organizational levels, although they’re most commonly used to manage capacity on team Kanban boards.
WIP limits can be implemented for the entire “in process” part of your Kanban board, for specific lanes, or both. There is no one correct way to implement WIP limits -- although a general rule is that they should be slightly constraining. They should force us to make decisions regarding the priority, time sensitivity, and cost of delay of various projects. If your team never hits its WIP limit, this is probably a sign that your WIP limit is too high.
If WIP limits are being applied across the team, a good starting place is the number of team members plus one -- so if you have 10 members working on a board, implement a WIP limit of 11 as a starting point.
Why We Need WIP Limits: The Common Culprits
WIP limits are difficult to implement because they seem counter-intuitive: Do less to get more done? But the truth is, if we can have the discipline to actively manage how much we are working on at any given time, at both the individual and team levels, we can gain the focus to get work done quickly, with high quality. This means that by doing less at a time, we can actually get more done.
There are many types of waste that WIP limits can help us proactively reduce and eliminate. Here are some of the most compelling reasons why we need WIP limits.
Context switching is what happens when we stretch our focus, time, attention, and brain power across too many objects in motion. When we juggle too many projects at once, we waste these precious resources transitioning between contexts, instead of adding value to work.
According to research done by Gloria Mark, Professor of Informatics at the UC - Irvine, it takes people an average of 23 minutes and 15 seconds to regain focus after even a brief interruption -- such as a “quick question” via Slack or an unsolicited conversation by the coffee maker. If we’re interrupted 5 times a day, that means we lose nearly 2 hours every day to context switching. Over the course of a week, that adds up to over 10 hours -- more than a full work day. Imagine the impact this has across an entire organization over the course of a year.
Context switching can also significantly impact our stress levels. In the same study, researchers gave two groups of workers a simple office task to complete: answering emails. One group was not interrupted during the task, while the other group received phone calls and IM messages. The interrupted group scored significantly higher on the NASA workload scale in terms of stress, frustration, mental effort, and mental workload.
How WIP Limits Can Help
WIP limits help teams reduce context switching by keeping individuals and teams focused on delivering just a few projects (as few as possible) at a time. Focus is what enables us to create high-quality work from start to finish. WIP limits train us to focus on moving things through to “Done” as quickly as possible, with as few distractions, delays, or handoffs as possible.
While we still have to discipline ourselves to limit other workplace distractions (email, Slack, conversations with coworkers), limiting the amount of work on our plate at any given time gives us the clarity and focus to deliver higher quality work faster -- while also reducing our stress.
Another unfortunate side effect of too much WIP is excessive meetings. When everyone on a team is juggling multiple projects at once, it becomes much more difficult to keep everyone on the same page. To gain alignment, a common solution is to have a status meeting -- to discuss what progress has been made, and what needs to be done next.
If meetings were a rarity on our calendars, we’d probably be better at them: Everyone would be aligned around an agenda, ready to discuss the pertinent issues. We’d make decisions with clarity and focus, then get back to actually delivering the work. Meetings are not inherently the problem.
The problem is, because we have too much WIP, most of our calendars are filled with status meetings. Many of us don’t even have time to prepare for these meetings during the normal work day. Because of this, it often takes the first half of the meeting to get everyone aligned on what is being discussed and what needs to be decided to move forward -- which means our meetings are longer, and less efficient, too.
If you consider the collective salary of everyone involved in a meeting, and what they could do if they instead spent that hour delivering focused, high-quality work, you’ll realize that status meetings come with a hefty price tag. Harvard Business Review released a Meeting Cost Calculator last year to estimate the cost of meetings. Crunch your own numbers to see how much your status meetings are costing your organization.
And of course, there’s also the logistical difficulty of scheduling meetings, which can result in significant delays. If everyone’s schedules are fully booked for weeks in advance, work might be delayed for weeks because the 5 people involved couldn’t find 30 minutes to get in a room together and make a decision. It’s worth considering: what’s the cost of delaying this piece of work for weeks at a time?
How WIP Limits Can Help
The visualization piece of Kanban alone helps to eliminate much of the need for status meetings. If a board is designed well, a card’s status is evident by its position on the board. Anyone who is interested in learning more about what progress has been made can open the card to look into card history, details, comments, and attachments.
WIP limits further reduce our need for excessive meetings. If any given team member is involved in 2-3 projects at a time, their calendar looks significantly different than if they are involved in, say, 7 projects. It’s easier to stay aligned around work when there are fewer objects in motion -- which means instead of spending our days in ineffective, costly meetings, we can spend our time delivering pieces of value across the finish line.
Rework and duplicate efforts are the unfortunate side effects of poor communication in teams. They are often a symptom of two concurrent factors: Too much WIP, and immature use of Kanban boards. Visualization is the first step to improving communication across a team, but if the team doesn’t adopt a systems thinking mentality, communication issues will not go away on their own.
Rework is what happens when work that is done does not satisfy business requirements. This can happen for a number of reasons:
- Data required to complete the work is inaccurate or incomplete.
- Business requirements shift while the work is being done.
- Business requirements are not clearly communicated before the work is started.
- External factors render the existing work useless and require it to be redone.
Similarly, duplicate effort is generally a sign of a communication breakdown. Often, it happens because team members begin work on a task without assigning themselves to it on the Kanban board. It can also happen if a task isn’t visualized on the board at all -- then no one knows that the task is being worked on, or who’s working on it.
The people working on the task might not realize that they need more information in order to satisfy the business requirements for that task -- which means not only is the effort duplicated, it might also need to be redone.
How WIP Limits Can Help
Each of these scenarios could be avoided through more effective communication, which starts by visualizing work and applying WIP limits. Visualizing work (and who’s assigned to it) helps communicate card assignments. WIP limits, when applied properly and managed as a team, enable a systems thinking approach that can help avoid these types of communication breakdowns.
Here’s how: Teams practicing Kanban who have implemented WIP limits will meet frequently to discuss the work on their board. The most common format for this is a daily standup, a short meeting in which the team discusses how to work together to move work across the board to “Done.” Because WIP limits constrain the amount of work that can be actively worked on at any given time, they force teams to have important conversations about work currently in motion. During standups, teams will ask questions like:
- What’s closest to being done? What can we do today to move it off the board?
- Is anyone working on anything that’s not on the board?
- Is anything currently blocked from making progress?
- Is anyone available to help move card X to “Done”?
These types of questions force teams to have important conversations about team priorities, opportunities for collaboration, and more, which can help teams avoid costly rework and duplicate effort.
When teams try to increase their speed of delivery with Kanban, they often try to reduce the amount of time it takes to complete each step in the process. This is based on the (often flawed) assumption that it’s the active work steps that are taking the most time to complete. In reality, work often spends much more time in the wait states between active steps than it spends actively being worked on.
Delays between active work steps are called handoff delays. They usually happen when a team and the individuals within it have too much WIP. If everyone is juggling multiple pieces of work, and contributing to those pieces of work at various steps, it becomes harder to coordinate efforts and keep momentum going.
How WIP Limits Can Help
WIP limits reduce handoff delays by limiting how much work the team can have in process at any given time. With less work items in motion, team members have greater opportunity to keep momentum moving on work. They also are able to more effectively communicate with each other about how to keep work moving, and can have the clarity to optimize their process for more effective, faster handoffs.
Stop Starting, Start Finishing
Visualization is a great first step toward optimizing flow, but if your team stops there, you aren’t truly practicing Kanban. The power of Kanban kicks in when teams begin using their board to actively manage and optimize flow for value delivery. This often involves breaking some habits -- like context switching, excessive meetings, and hidden WIP -- that are deeply ingrained in the way we work.
WIP limits can provide the discipline, structure, and opportunities for communication that we need to be able to see and eliminate our most costly sources of waste. They teach us how to stop starting and start finishing -- because ultimately, work has no value until it is in the hands of the customer. Although WIP limits might seem painful and counterintuitive at first, they are necessary to unlock the true potential of our teams, and can enable us to be more effective, communicative, and collaborative than ever before.