Calculators
WIP Inventory Calculator
Calculate ending work-in-process inventory value, WIP turnover and average flow time using Little's Law.
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The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Month-end inventory valuation
- Lean flow analysis
- Lead time reduction
- Cost accounting coursework
About this tool
What the WIP Inventory Calculator does
Work in process (WIP) is inventory that has entered production but is not yet finished. Its value is beginning WIP plus manufacturing costs minus the cost of goods completed. Little’s Law links WIP, throughput and flow time: average WIP equals throughput times flow time.
It also works as a work in process calculator.
Formula
- Ending WIP = beginning WIP + manufacturing costs − cost of goods completed
- Flow time = average WIP units ÷ throughput (Little’s Law)
- WIP turnover = cost of goods completed ÷ average WIP
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Beginning WIP | $85,000 |
| Manufacturing costs this period (materials, labour, overhead) | $420,000 |
| Cost of goods completed | $430,000 |
| Average units in WIP | 1,800 |
| Units completed per day | 400 |
| Result | Value |
|---|---|
| Ending WIP | $75,000 |
| Average flow time (Little’s Law) | 4.5 days |
| WIP turnover for the period | 5.38 |
How to read the result
Reducing WIP shortens flow time without slowing output, which is why lean systems cap WIP.
High WIP often hides quality problems and makes priorities unclear on the shop floor.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Goods in production that are not yet finished.
Average inventory in a system equals throughput multiplied by average time in the system.
Lower WIP shortens lead times, frees cash and exposes problems.
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