Little's Law calculator
Use Little's Law to find work in process, throughput or lead time when you know the other two.
How it is calculated
Little's Law: WIP = throughput × flow time. Solve for the missing value: flow time = WIP ÷ throughput, or throughput = WIP ÷ flow time.
Worked example
WIP = 120 units and throughput = 20 units per day: flow time = 120 ÷ 20 = 6 days.
Steps
- Enter the two values you know.
- Leave exactly one field empty.
- Read the value of the empty field, in the same time unit you used.
Frequently asked questions
Which time unit should I use?
Use the same unit for throughput and flow time, such as days or hours. Little's Law needs them to match.
Does it work for any process?
It holds for stable systems over a long period, where the WIP and throughput are averages.
Why is it useful?
It links inventory, speed and throughput. Reducing WIP on a steady line cuts lead time directly.
Related calculators
References
Little (1961), A Proof for the Queuing Formula L = λW; see also Hopp and Spearman, Factory Physics.
Estimates for information only. Verify critical values with a qualified engineer or your supplier standards.