Lean Manufacturing & Operations worked example

Queue Time Estimate with units waiting in queue ahead of 6 units: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop units waiting in queue ahead to 6 units, then walk the calculation through step by step. Estimate queue time (wait before processing) by multiplying WIP ahead in queue by the cycle time of the downstream station.

The inputs for this scenario

  • Units waiting in queue ahead: 6 units (the input this scenario stresses; the baseline uses 12)
  • Station cycle time per unit: 3 min (held at the documented default)
  • Queue variability factor: 1.2 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Queue Time = Units in Queue x Station Cycle Time x Variability Factor.
  • Estimated queue time works out to 21.6 min at these inputs, and this is the headline figure for the scenario.
  • Base product works out to 21.6 value at these inputs.
  • Multiplier works out to 1 x at these inputs.
  • Factor A x B works out to 18 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where units waiting in queue ahead sits at 12 units and the headline result is 43.2 min, this scenario comes in 50% below the baseline at 21.6 min.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to units waiting in queue ahead, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It is a deterministic approximation; true queue behavior follows queuing theory and grows sharply as utilization nears 100%, which a single linear factor cannot fully capture.

Results at a glance

  • Estimated queue time: 21.6 min (headline result)
  • Base product: 21.6 value
  • Multiplier: 1 x
  • Factor A x B: 18 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Queue Time Estimate calculator, set units waiting in queue ahead to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.