Assumptions and method
Use the same system boundary and period, with stable long-run averages. This is not a guaranteed date for one item.
Test a scenario
Use the result in a decision
Use consistent workflow boundaries and observation periods.
Use the same system boundary and period, with stable long-run averages. This is not a guaranteed date for one item.
Set a baseline and change one assumption to compare outcomes.
A worked example
Follow the fixed teaching example
- Use the same workflow boundary and period for both averages.
- Average cycle time = 12 items / 3 items per day = 4 days.
These illustrative inputs describe a project scenario, not a published benchmark. All monetary inputs use the same currency and price basis.
- Average work in progress (items)
- 12
- Average throughput (items/day)
- 3
- Implied average cycle time
- 4 days
Interpret the output only within the assumptions above. Changing the inputs changes the result; it does not validate the inputs.
Source & credit
John D. C. Little, A Proof for the Queuing Formula: L = λW (1961).
John D. C. Little (1961): original proof
This is independently written code and explanation of the underlying method. The linked publication, its diagrams and its trademarks remain its owner’s material; no permission to reuse them is implied.