WIP limits: how to set them and what to do at the limit

WIP stands for work in progress: everything that's been started and not finished. A WIP limit is a number on a column, such as In Progress (3), that says how many cards may be in it at once.

It's the rule that turns a board into kanban. Without limits, a board shows the work. With them, it changes how the work flows.

• Less switching. Every extra thing on the go costs time to pick back up. 3 things in progress get more attention each than 9.
• Things finish. Finished work is worth something; 9 half-done pieces are worth nothing until they're done.
• Problems surface. When a column is full and stuck, everyone can see it, and the team has a reason to fix what's blocking it rather than start around it.
• Shorter cycle time. Little's Law: at the same pace of work, fewer cards in progress means each card takes less time. See cycle time vs lead time.

There's no perfect number to start with. Pick a reasonable one and adjust it.

1. Start with the people. For In Progress, try the number of people working from the column, or that number plus 1. A team of 4 might start at 4 or 5.
2. Limit the waiting columns too. A Review or Testing column with no limit fills up quietly. A limit of 2 or 3 makes reviews happen.
3. Leave To Do and Done alone. The limit belongs on the columns where work is being done or waiting to be checked.
4. Run it for 2 weeks. If the limit is hit every day and people sit idle, raise it by 1. If it's never reached, lower it by 1.

This is the moment the limit exists for. Instead of starting something new:

• Help finish what's there. Pair on a card, review someone's work, or test what's waiting.
• Clear the blocker. If a card is stuck on someone outside the team, chase it.
• Look downstream. A full In Progress column is often caused by a full Review column after it.
• Break the limit only on purpose. An urgent card can go over the limit, but say so out loud, and treat it as the exception.

• Limits nobody keeps. A number that's always exceeded is decoration. Lower your ambitions or raise the number.
• Hiding work. Starting things off the board to stay under the limit defeats the point.
• Limits that are too high. A limit of 20 on a team of 4 never bites, so nothing changes.
• Setting it once and forgetting it. Teams change. Revisit the number when the team or the work does.

Any column on a craaft board can have a WIP limit: edit the column and set its card limit. The column's header shows the count against the limit, as in 3 of 4, and turns red when the column is full.

craaft doesn't block a move into a full column. The limit is a signal for the team, so an urgent card can still go in, and everyone can see that it did. Start from the kanban board template and give In Progress a limit.