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Little's Law WIP & Flow Time Calculator
Estimate average time in a stable process from average work in process and long-run throughput on the same process boundary.
Little's law flow time calculator
Estimate average time in a stable process from average work in process and long-run throughput on the same process boundary.
YOUR RESULT LIVE CALCULATION
Average time inside the process
4hours
COMPATIBLE LONG-RUN AVERAGESOne less spreadsheet to keep open.
- Average flow time
- 240 minutes
- Average work in process
- 240 units
- Average completed throughput
- 60 units/hour
Includes waiting and processing within the same boundary. This is an average, not a promised completion time for a particular unit.
BEHIND THE NUMBER
How the calculation works
Use compatible long-run averages for the same item population and process boundary, including queues inside that boundary. WIP includes units waiting and being processed. Throughput is the actual average completion rate, not nameplate capacity. This is the L = throughput x flow time relationship rearranged for average flow time.
Average flow time (hours) = average WIP / average throughput per hour
When this calculation helps
Little's law relates average work in process, throughput, and flow time over a consistent system boundary. It helps test whether an observed queue and output rate imply a plausible elapsed time.
Check the interpretation
Use compatible units and a reasonably stable flow. Mixing a peak queue with an unrelated average throughput produces a misleading estimate. This relationship does not identify individual job priorities or guarantee the lead time of the next order.
This is not an individual-order due date or percentile waiting-time estimate. A growing or draining backlog, mismatched time windows, inconsistent boundaries, or mixed unit definitions can invalidate the interpretation.
MIT queueing models and Little's lawGood to know
Is the result processing time only?
No. It includes all time within the chosen process boundary, including queueing, provided WIP and throughput use that same boundary.
Can I use planned maximum output?
Use actual long-run average throughput. Substituting theoretical maximum capacity can understate flow time.