Little's Law: Why Adding More Work Slows You Down
Little's Law shows that average task completion time is proportional to the work in progress (WIP). For a stable team, Cycle Time = WIP / Throughput. It's used in Kanban to predict delivery times. The footgun is adding more WIP to go faster; this always.
THE MENTAL MODEL: The more tasks you have in progress at once, the longer each individual task will take to finish. Think of a highway: adding more cars (Work in Progress) doesn't make anyone go faster; it eventually slows everyone down (increases Cycle Time). Little's Law provides the mathematical proof for this intuition.
HOW IT WORKS: The law is expressed as L = λ * W. In software development terms, this translates to: Average Work in Progress (L) = Average Throughput (λ) * Average Cycle Time (W). The most useful version for teams is rearranged: Cycle Time = WIP / Throughput. If your team consistently has 15 tasks in its 'in progress' columns and historical data shows you complete 3 tasks per week, you can predict that the average task will take 5 weeks to get through the system (15 / 3 = 5).
WHEN TO USE IT: Use Little's Law to make informed decisions about your process. It's the mathematical foundation for setting WIP limits in Kanban. It allows you to forecast average delivery times based on stable, historical data. It's also a powerful tool to explain to stakeholders why you can't just 'take on one more thing' without impacting all other delivery dates.
WHEN NOT TO USE IT: The law relies on long-term averages in a stable system. If your team size, process, or the nature of your work changes dramatically, your historical averages for throughput become invalid. It also predicts the average, not the outcome for any single task. Do not use it to promise a specific delivery date for a specific feature, as outliers are common.
ONE CANONICAL EXAMPLE: An engineering team has a strict WIP limit of 8 tickets. Their data from the last six months shows they consistently complete 2 tickets per week (their throughput). A product manager asks for the average time it takes for a new ticket to be completed. Using Little's Law: Cycle Time = 8 tickets / 2 tickets per week = 4 weeks. If the team wants to reduce that 4-week average, the law shows they have only two levers: reduce the WIP limit below 8, or find a way to increase throughput to more than 2 tickets per week.
Read the original → en.wikipedia.org
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