Material Cost per Productive Hour Formula
Learn how to calculate direct material cost per productive labour hour using inventory, purchases, freight and purchase reductions.
This calculation estimates how much direct material cost is allocated to each productive labour hour in a period. It can support internal costing and profitability reviews when inventory values, purchases and hours are measured consistently.
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Material Cost per Productive Hour
Where:
First find the materials consumed during the period by adjusting purchases, adding opening inventory and subtracting closing inventory. Then divide the materials used by productive labour hours.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| openingMaterialInventory - Opening material inventory | Value of material inventory held at the beginning of the accounting period. | currency |
| materialPurchases - Material purchases | Materials bought during the period before returns, rebates and discounts. | currency |
| freightIn - Freight and delivery cost | Inbound delivery or freight cost that is part of acquiring materials. | currency |
| purchaseReturnsDiscounts - Purchase returns and discounts | Supplier returns, rebates or discounts that reduce purchase cost. | currency |
| closingMaterialInventory - Closing material inventory | Value of material inventory remaining at the end of the period. | currency |
| productiveLaborHours - Productive labour hours | Hours directly associated with production or job work in the same period. | hours |
Step-by-Step Calculation
Calculate net material purchases
Add inbound freight to purchases, then subtract returns, rebates and discounts.
netMaterialPurchases = materialPurchases + freightIn - purchaseReturnsDiscounts
Calculate materials available for use
Combine opening inventory with adjusted purchases made during the period.
materialsAvailable = openingMaterialInventory + netMaterialPurchases
Calculate direct materials used
Subtract materials still on hand at period end to estimate materials consumed.
materialsUsed = materialsAvailable - closingMaterialInventory
Allocate material cost across productive hours
Divide direct materials used by the productive hours recorded for the same period.
materialCostPerHour = materialsUsed / productiveLaborHours
Monthly workshop material costing example
Net material purchases
$25,000 + $1,200 - $500
$25,700
Materials available for use
$5,000 + $25,700
$30,700
Direct materials used
$30,700 - $6,200
$24,500
Material cost per productive hour
$24,500 / 1,600
$15.3125 per hour
Final Result
Estimated direct material cost per productive hour: $15.31.
Assumptions
- ✓All inventory, purchase and labour-hour figures cover the same accounting period.
- ✓Opening and closing inventory are valued using a consistent inventory valuation basis.
- ✓Freight in is a material acquisition cost rather than a separate operating expense.
- ✓Productive labour hours reasonably share the direct materials used.
Limitations
- !The result is an allocation estimate and may not match material cost on an individual job or product.
- !Stock losses, spoilage, write-downs, transfers and inventory count corrections may need separate treatment.
- !The calculation does not include direct labour, manufacturing overhead, tax or profit margin.
- !Different inventory valuation or cost-allocation methods can produce different results.
Common Mistakes to Avoid
Using total payroll or attendance hours instead of hours directly related to production or jobs.
Including outbound shipping costs as freight in when they are not acquisition costs.
Subtracting purchase discounts twice if purchase figures are already recorded net of discounts.
Using opening and closing inventory values prepared on inconsistent valuation methods.
Combining inventory figures from one period with productive hours from another period.
Related Formulas
Frequently Asked Questions
What is the formula for material cost per productive hour?
Divide direct materials used by productive labour hours. Direct materials used equal opening inventory plus purchases plus freight in, less returns, discounts and closing inventory.
Why is closing material inventory deducted?
Closing inventory remains available at the end of the period. Deducting it removes material that was acquired but not consumed.
Are purchase returns and supplier discounts subtracted?
Yes. They reduce the net cost of materials acquired, provided they have not already been deducted from the purchase figure entered.
Should productive hours include idle time?
This depends on the costing method used. For a direct production allocation, productive job or production hours are generally the relevant base.
Does hourly material cost include labour cost?
No. It measures direct material cost only. Labour and overhead need separate calculations if they are relevant to the costing review.
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