Work-In-Process (WIP) Calculator

Work-In-Process (WIP) Calculator

How much partially-completed inventory is sitting in your production system right now, expressed in terms of days of output? This calculator applies Little's Law to find out.

WIP Days = Units in Production System / Average Daily Output

Example

500 units currently in the production system, averaging 250 units of daily output:

WIP Days = 500/250 = 2.0 days of WIP inventory

Why Excess WIP Is a Problem

Too much WIP ties up capital, floor space, and often masks underlying process problems - like an unbalanced line with a hidden bottleneck station - since excess buffer inventory between stations can hide the fact that one station is chronically slower than the others.

Why Too Little WIP Is Also a Problem

Conversely, too little WIP can starve downstream stations of work whenever upstream variability occurs (a machine hiccup, a quality hold, a supply delay), causing avoidable idle time further down the line. Lean manufacturing principles generally favor minimizing WIP to the lowest level that still keeps the line running smoothly - excess WIP beyond that point is considered one of the classic forms of manufacturing waste.