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WIP Limit Calculator

Work out wip limit instantly with clear inputs, formula shown and shareable results.

About WIP Limit Calculator

Little's law fixes the relationship: WIP = throughput x lead time. To hit a lead time target at a given throughput, WIP must be capped at their product. Any WIP above that cap adds queue time without adding output, which is why current lead time can be read straight off current WIP.

Formulas

Little's law

WIP = throughput x lead time; lead time = WIP / throughput

Station cap

WIP per station = WIP limit / number of stations

Worked example

With the default values below, WIP Limit Calculator returns WIP Limit of 480. Change any input above and every figure here is recalculated in your browser.

Inputs used

Target Throughputminimum 0.01 units/hour
120 units/hour
Target Lead Timeminimum 0.01 hours
4 hours
Process Stationsminimum 1
6
Current WIPminimum 0 units
700 units

Results

WIP Limit
480
WIP Cap Per Station
80.00
Lead Time At Current WIP
5.833
Excess WIP To Remove
220

Step by step

  1. 1Values used
  2. 2Little's law
  3. 3Station cap
  4. 4WIP Limit= 480
  5. 5WIP Cap Per Station= 80.00
  6. 6Lead Time At Current WIP= 5.833
  7. 7Excess WIP To Remove= 220

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Does cutting WIP reduce output?

Not until WIP falls below the level needed to keep the bottleneck fed. Above that, extra WIP only lengthens queues. The productive range is usually far lower than intuition suggests.

Where should the WIP cap be enforced?

At the release point into the line. Capping release is what actually controls WIP; capping downstream just moves the queue.

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