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Team Operations

Little’s Law connects work in progress, throughput and lead time

Editors at Work in Practice ·
A small team looking at a simple work board with three columns and plain cards, no readable corporate information.
AI-generated photographic illustration; not documentary photography.

A team can look busy while finished work arrives slowly. Counting active tasks shows how much work is inside the process, but it does not explain how long a typical item spends there. Little’s Law connects these quantities through an average relationship.

In a stable process, average work in progress equals average throughput multiplied by average time in the system. MIT’s explanation of John Little’s work describes the relationship’s broad importance. Its usefulness in a team depends on defining a system that you can actually measure.

A small numerical example

Imagine a review service with an average of 12 items between “accepted for review” and “review complete”. If it completes an average of three comparable items per working day under stable conditions, the relationship gives an average time inside that boundary of four working days: 12 divided by three.

This is an illustrative calculation. It does not promise that the next item will finish in four days. Some may move quickly while others wait, and a sudden arrival surge can make the recent averages a poor description of the next week.

  1. Draw the start and finish boundaries. Include waiting inside them, not just hands-on effort.
  2. Count work consistently. A ticket, a customer request and an entire project are different units.
  3. Use a compatible time basis for throughput and duration.
  4. Check whether arrivals, completions and the amount of work are reasonably stable over the observation period.

MIT’s lean-process teaching materials place this relationship alongside process-flow thinking. That context matters: the equation describes averages, while changes to capacity, queues and priorities require investigation.

Use the calculation to ask a better question

If work in progress rises without a matching increase in completions, examine where items accumulate. Are approvals waiting for one person? Is work entering before the required information is available? Are urgent tasks repeatedly displacing ordinary ones?

Do not assume that removing half the team or closing half the tickets will produce a mathematically guaranteed improvement. Changing the process can also change throughput and the mix of work. Record a baseline, make a considered adjustment and observe what happens to both delivery and quality.

For a management conversation, a clearly bounded average is more useful than a demand that everyone move faster. It points attention towards the work’s journey through the system, including the time nobody is actively touching it.

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