Working Capital Per-Unit Formula
Learn how to calculate estimated working capital per unit from production costs, inventory days, customer payment days, and supplier credit.
This formula estimates the average operating cash tied up for each planned unit of output. It combines raw materials, work in progress, finished goods, and receivables, then deducts supplier credit to show an estimated net funding requirement.
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Working Capital Per Unit
Where:
Estimate each amount tied up per unit during the year, add inventory and customer balances, then subtract the value of supplier credit.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| M - Material cost per unit | Direct material and purchased-component cost for one completed unit. | currency |
| C - Conversion cost per unit | Direct labour and production overhead cost for one completed unit. | currency |
| RM - Raw material holding days | Average days materials are held before entering production. | days |
| WIP - Work in progress days | Average days units remain partly completed in production. | days |
| P - Average WIP completion | Average proportion of total production cost incurred by work in progress. | percent |
| FG - Finished goods holding days | Average days completed goods are held before sale. | days |
| S - Selling price per unit | Credit sales value for one unit, before sales taxes where possible. | currency |
| R - Customer payment days | Average days customers take to pay after a credit sale. | days |
| AP - Supplier credit days | Average days allowed to pay suppliers for materials. | days |
| U - Annual units sold | Expected annual production and sales volume used to calculate the total requirement. | number |
Step-by-Step Calculation
Calculate production cost per unit
Add material cost to labour and production overhead for a completed unit.
productionCostPerUnit = materialCostPerUnit + conversionCostPerUnit
Estimate raw material investment
Value average raw material stock at direct material cost.
rawMaterialInvestment = annualUnits * materialCostPerUnit * rawMaterialDays / 365
Estimate work in progress investment
Value partly completed units using the selected average completion level.
workInProgressInvestment = annualUnits * productionCostPerUnit * workInProgressDays / 365 * wipCompletionPercent / 100
Estimate finished goods and receivables
Finished goods use production cost, while receivables use the credit sales value.
finishedGoodsInvestment = annualUnits * productionCostPerUnit * finishedGoodsDays / 365; receivablesInvestment = annualUnits * sellingPricePerUnit * receivableDays / 365
Deduct supplier credit
Supplier balances reduce the amount of cash the business must provide.
supplierCredit = annualUnits * materialCostPerUnit * payableDays / 365
Calculate total and per-unit working capital
Divide estimated net operating working capital by planned annual output to express it per unit.
totalWorkingCapital = rawMaterialInvestment + workInProgressInvestment + finishedGoodsInvestment + receivablesInvestment - supplierCredit; workingCapitalPerUnit = totalWorkingCapital / annualUnits
Example: Manufacturer planning 12,000 annual units
Production cost per unit
$25.00 + $15.00
$40.00
Raw materials less supplier credit
12,000 × $25.00 × 30 / 365 − 12,000 × $25.00 × 30 / 365
$0.00 net
Work in progress
12,000 × $40.00 × 10 / 365 × 50 / 100
$6,575.34
Finished goods
12,000 × $40.00 × 20 / 365
$26,301.37
Receivables
12,000 × $55.00 × 45 / 365
$81,369.86
Total and per-unit requirement
($6,575.34 + $26,301.37 + $81,369.86) / 12,000
$9.52 per unit
Final Result
Estimated working capital is $114,246.58 in total, or $9.52 per planned annual unit. The simple net operating cycle is 75 days.
Assumptions
- ✓Annual production and sales occur evenly across a 365-day year.
- ✓Raw materials and supplier credit are measured using direct material cost only.
- ✓Work in progress is valued at the selected average completion percentage of total production cost.
- ✓Finished goods are valued at production cost and receivables at credit selling price.
- ✓The calculation covers operating inventory, receivables, and supplier payables only.
Limitations
- !Seasonal buying, production peaks, and uneven sales can create funding needs different from the annual average.
- !Actual customer collections, stock losses, returns, and supplier payment timing may differ from the entered days.
- !The formula excludes cash reserves, taxes, selling expenses, loans, interest, and other current assets or liabilities.
- !A single average WIP completion percentage may not represent complex or multi-stage production.
Common Mistakes to Avoid
Entering selling price instead of material cost when valuing raw materials or supplier credit.
Valuing finished goods at selling price rather than production cost.
Using a WIP completion percentage above 100% or treating it as a decimal when the input expects a percentage.
Using calendar payment terms rather than the average time customers actually take to pay.
Assuming the per-unit result is a cash cost; it represents estimated funds tied up, not an additional production expense.
Related Formulas
Frequently Asked Questions
What is the working capital per-unit formula?
It adds per-unit funding tied up in raw materials, WIP, finished goods, and receivables, then subtracts per-unit supplier credit. Each component is based on its relevant annual value and days divided by 365.
Why does annual output not appear in the simplified per-unit formula?
When output is assumed to be steady, annual units are used in both total working capital and the division back to per unit, so they cancel out. Annual units still determine the total funding requirement.
How is work in progress valued in this calculation?
WIP is valued using total production cost multiplied by WIP days and the average completion percentage. A 50% completion input treats average WIP as having incurred half of total production cost.
How is the net operating cycle calculated?
Net operating cycle days equal raw material days plus WIP days plus finished goods days plus customer payment days, less supplier credit days.
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