Little’s Law Calculator
Solve average work in process, throughput or flow time with Little’s law, keeping the throughput time basis explicit.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert the entered throughput to items per second and flow time to seconds. Apply the steady-state identity L=λW and rearrange only when the selected output is unknown.
L=λW; λ=L/W; W=L/λ
Worked example
An average throughput of 4 items per hour and average flow time of 5 hours imply 20 items in the system. Twenty items with a 5-hour flow time imply 4 items per hour.
Assumptions and input details
Long-run stable averages over the same system boundary and period. Items in service and waiting both belong in L; W is total time within that boundary. This identity does not predict variability, queue percentiles, capacity, service distributions or individual completion time. Positive divisors are required when solving a ratio.
References: MIT OpenCourseWare: Little’s law
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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