What does Little's law say and how does it apply to an IT department?
Little's law states that, in a stable system, work in progress equals throughput multiplied by average lead time (WIP = throughput × lead time). For an IT department with constant throughput, doubling the number of parallel projects therefore doubles each project's average lead time: limiting work in progress is the most direct way to shorten deadlines.
Little's law applied to an IT department
The more projects you open at once, the longer each one takes.
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Formula
- Work in progress = throughput × average lead time.
- Average lead time = work in progress ÷ throughput.
- Assumption: stable system, constant average throughput over the period.
Worked example
A team completes an average of 2 projects per month. With 6 projects in parallel, the average lead time is 6 ÷ 2 = 3 months. With 12 projects in parallel and the same throughput, it rises to 6 months. Opening more projects did not increase what the team finishes; it only lengthened each one's wait.
IT applications
- Limit the number of active projects per team instead of accepting every request.
- Use net capacity to decide how many projects to start.
- Arbitrate in committee by accepting a project only if another finishes or is postponed.
FAQ
Does Little's law apply to uneven projects?
Yes, in averages over a stable period. It gives an order of magnitude, not an exact forecast project by project.
How do you measure an IT department's throughput?
By counting projects, or deliverables, completed per month over several months.
Is this an argument to refuse projects?
It is an argument to sequence them: starting fewer projects at a time finishes them sooner.
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