Little's Law

"For a given process, in general, the more things that you work on at any given time (on average) the longer it is going to take for each of those things to finish (on average)."

Little's Law

(W = L / λ)
Average Cycle Time = Average Work in Progress / Average Throughput

Little's Law is a mathematical theorem that describes the relationship between the average number of items in a system, the average arrival rate of items, and the average time an item spends in the system.

In the context of Agile, Little's Law explains the dynamics of workflow in a system, such as a Scrum or Kanban team, and highlights the importance of managing Work in Progress (WIP) to ensure smooth delivery. If the WIP becomes too high, cycle time increases, causing delays, bottlenecks, and reduced throughput.

Scenario

Imagine a Scrum team working on a Kanban board with these parameters:

  • The team processes 5 user stories per week (arrival rate, λ = 5 stories/week)
  • The average cycle time for a user story is 2 weeks (W = 2 weeks)

Using Little's Law:
L = λ * W
L = 5 stories/week * 2 weeks = 10 stories

This means the team can only handle 10 stories in progress at any given time. If the team takes on more stories than this limit, the cycle time will increase due to overload, slowing down the delivery of individual stories.

How Agile Teams Can Apply Little's law:
  • Limit WIP:
    • By capping WIP, teams can ensure smoother workflows and faster cycle times.
  • Optimize Throughput:
    • Focus on completing work before starting new work to improve flow.
  • Track Metrics:
    • Regularly measure and monitor cycle time and throughput to identify bottlenecks.
  • Balance Workload:
    • Avoid overloading team members, ensuring the WIP is in proportion to the team's capacity.

Summary

Start Less, Finish More

By understanding and leveraging Little's Law, Agile teams can maintain better control over their workflows and deliver value more predictably.