kanban vs. To-do Lists and Scrum

A kanban board for a blog application development project. The numbers next to column titles are Work In Progress (WIP) limits.

kanban is a system originally developed by Toyota to reduce waste.

Key Benefits:


Comparison:

to-do kanban
Single phase
(just a list of checkboxes)
Multiple phases
(Backlog, To-do, In-progress, Done)
Does not prevent working on all tasks at the same time Work In Progress (WIP) limits
bring focus, reduce cycle times
No way to reliably track time spent on each task Time spent on each task in each phase is tracked
Estimates are manual and error-prone Current cycle time is a reliable indicator of future performance








Scrum kanban
Multiple phases Multiple phases
Requires timeboxes (sprints) usually
2 to 4 weeks long
Continuous flow
Does not prevent working on all tasks at the same time Work In Progress (WIP) limits
bring focus, reduce cycle times
Does not allow changes when a sprint is in progress Changes can be made any time
Requires manual estimates for
each task
Current cycle time is a reliable indicator of future performance

A to-do list is a simple way to manage a project. On a to-do list, a task is either done or not. In reality, things are rarely that simple. What happens in between is completely missing from the picture.

To-do lists do not have kanban's Work In Progress (WIP) limits. When there is no limit on the number of tasks that can be worked on simultaneously, your team loses focus, and everything gets longer to complete. WIP limits allow you to discover the optimal throughput for your team. With the right WIP limits, you can avoid tasks piling up, and balance demand against your team's capacity.

There is no reliable way to measure the time spent on each task in the absence of kanban's multiple phases and WIP limits. Due-date estimates are also problematic because of the tendency to add "safety buffers". Eventually these buffers add up, and everything gets longer and longer to complete.

Scrum addresses some of the shortcomings of to-do lists. It supports multiple phases, and instills a sense of urgency with its sprint concept, but it falls short in a number of areas.

In Scrum, a number of tasks are chosen for each sprint, and the team makes estimates for each task beforehand. Once a sprint is in progress, no changes are allowed. In reality, that does not work quite well. Since estimates are after all just educated guesses, you have to work extra when you are behind, and you waste time when you are ahead.

There are no WIP limits in Scrum. There is nothing to prevent a team to work on everything simultaneously, leading to many tasks in different states of completion.

kanban solves the problems inherent in to-do lists and Scrum by introducing WIP limits, and eliminating estimates and rigid timeboxes. The result is a smoothly flowing system that is both flexible and robust.


Related Article:
How kanban can help you increase your team's capacity

© 2010-11 Aycan Gulez