Conveyors worked example

Little's Law WIP for Conveyor Lines at 99% flow uptime factor: a worked example

What does the result look like when flow uptime factor reaches 99%? The full calculation is worked below with real intermediate numbers. an industrial engineer needs to check whether observed WIP matches line throughput and lead time

The inputs for this scenario

  • Line throughput rate: 520 units / period (unchanged)
  • Average line lead time: 1.8 periods (unchanged)
  • Flow uptime factor: 99 % (raised for this scenario; the documented default is 92)
  • Usable WIP yield: 99 % (unchanged)

Working through the calculation

  • Applying the documented formula (Gross Little's Law WIP = throughput rate × lead time) to the inputs above produces each figure below.
  • At this operating point the engine returns 917 WIP units for estimated line wip, the number this scenario is built around.
  • At this operating point the engine returns 936 WIP units for gross little's law wip.
  • At this operating point the engine returns 9.36 WIP units for wip impact from flow downtime.
  • At this operating point the engine returns 9.27 WIP units for wip impact from unusable units.

How this compares with the baseline

  • Against the tool's baseline example, where flow uptime factor sits at 92% and the headline result is 853 WIP units, this scenario comes in 7.61% above the baseline at 917 WIP units.
  • A figure at this level is achievable when flow uptime factor is genuinely sustained, not just peaked for a shift. Little's Law assumes a stable system in steady state; during ramp-up, changeovers, or demand spikes the actual WIP will diverge from the estimate.

Results at a glance

  • Estimated line WIP: 917 WIP units (headline result)
  • Gross Little's Law WIP: 936 WIP units
  • WIP impact from flow downtime: 9.36 WIP units
  • WIP impact from unusable units: 9.27 WIP units

Run it with your numbers

  • Every input above is editable in the live Little's Law WIP for Conveyor Lines calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.