Process Costing: Methods, Weighted Average, FIFO, Equivalent Units

TAKEAWAYS:

• Process costing is used for mass production where identical units flow through sequential processes (e.g., sugar mills, textile factories, or NTC’s cable manufacturing).
• Equivalent units convert partially completed units into "full" units for cost allocation (e.g., 50% complete = 0.5 equivalent units).
• The weighted average method blends beginning inventory costs with current period costs, while FIFO treats beginning inventory separately (like a first-in-first-out inventory system).
• Abnormal spoilage is treated as a period cost, while normal spoilage is allocated to good units (e.g., broken tiles in a brick factory).
• By-products (e.g., sawdust from timber processing) are valued separately and reduce the cost of main products.
• Cost reconciliation ensures total costs (materials, labor, overhead) equal the sum of costs assigned to good units, spoilage, and ending inventory.

1. What is Process Costing?

Process costing is a cost accounting method used in industries where identical units are produced continuously through sequential processes (e.g., oil refining, cement manufacturing, or Nepal’s Shivam Cement Ltd.). Unlike job costing (where each unit is unique), process costing averages costs across all units produced in a process.

When to Use Process Costing?

Real-World Example:

• Shivam Cement Ltd. (Nepal) uses process costing to allocate costs (raw materials like limestone, labor, and overhead) across thousands of cement bags produced daily. Each process (crushing, grinding, packing) incurs costs that must be distributed fairly.

2. Key Terms in Process Costing

3. Equivalent Units of Production (EUP)

Since not all units are 100% complete at the end of a period, we calculate equivalent units to allocate costs accurately.

Formula:

$$\text{Equivalent Units}=\text{Units Completed}+\left(\text{Ending Inventory}\times \text{Percentage Completion}\right)$$

Example: A Nepalese sugar mill processes sugarcane into sugar. At the end of June, the Refining Process has:

• 500 kg of sugar completed and transferred out.
• 200 kg of sugar in ending inventory, 70% complete.

Calculation: $$\text{EUP}=500+(200\times 0.70)=500+140=640\text{ kg}$$

Visualization:

4. Methods of Process Costing

Two primary methods allocate costs differently:

A. Weighted Average Method

• Blends beginning inventory costs with current period costs.
• Formula: $$\text{Total Cost per EUP}=\frac{\text{Total Costs (Beginning + Current)}}{\text{Total EUP}}$$
• Advantage: Simple, smooths out cost fluctuations.
• Disadvantage: Ignores the age of inventory (old vs. new costs).

B. FIFO (First-In-First-Out) Method

• Treats beginning inventory separately from current costs.
• Formula:
  1. Allocate beginning inventory costs to units completed from prior period.
  2. Allocate current period costs to remaining EUP.
• Advantage: More accurate for inflationary periods.
• Disadvantage: Complex, requires tracking beginning inventory separately.

Comparison Table:

5. Worked Example: Process Costing for a Nepali Brick Factory

Scenario: Kathmandu Bricks Ltd. produces bricks in three processes:

1. Molding (clay shaping)
2. Drying (sun/oven drying)
3. Firing (kiln baking)

Data for June 2024 (Molding Process):

• Beginning Inventory: 5,000 bricks, 40% complete, costing NPR 20,000.
• Started in June: 50,000 bricks.
• Completed & Transferred Out: 45,000 bricks.
• Ending Inventory: 10,000 bricks, 60% complete.
• Costs Incurred in June:
  • Materials: NPR 150,000
  • Labor: NPR 80,000
  • Overhead: NPR 50,000

Step 1: Calculate Equivalent Units (EUP)

Step 2: Total Costs to Allocate $$\text{Total Costs}=\text{Beginning Inventory}+\text{Current Costs}=20,000+(150,000+80,000+50,000)=\text{NPR 300,000}$$

Step 3: Cost per EUP (Weighted Average) $$\text{Cost per EUP}=\frac{300,000}{51,000}=\text{NPR 5.88 per brick}$$

Step 4: Allocate Costs

Step 5: Cost of Goods Transferred to Drying Process $$\text{NPR 264,600}$$

6. Handling Spoilage and By-Products

A. Spoilage

• Normal Spoilage: Allocated to good units (e.g., 5% of bricks cracked in firing).
• Abnormal Spoilage: Treated as a loss (e.g., kiln explosion causing extra waste).

Example: If Kathmandu Bricks Ltd. has 5% normal spoilage in the Firing Process:

• Good Units Produced: 47,500 bricks (out of 50,000 started).
• Spoilage Cost: Allocated to remaining 47,500 bricks.

B. By-Products

Secondary products (e.g., rice bran from a mill) reduce the cost of the main product.

Example: A Nepalese rice mill produces 1 ton of rice and 50 kg of bran (sold for NPR 2,000).

• Bran Revenue: Deduct from rice production cost.
• Adjusted Cost of Rice: $$\text{Total Cost}-\text{Bran Revenue}=\text{NPR 50,000}-2,000=\text{NPR 48,000}$$

7. Process Costing vs. Job Costing

8. The Accounting Cycle in Process Costing

flowchart TD
    A["1. Record Costs Incurred"] --> B["2. Calculate EUP"]
    B --> C["3. Allocate Costs (Weighted Avg/FIFO)"]
    C --> D["4. Prepare Process Cost Summary"]
    D --> E["5. Transfer Costs to Next Process"]
    E --> F["6. Close Process Account"]
    F --> G["7. Report in Financial Statements"]

Key Documents:

1. Process Cost Summary Sheet (like a mini income statement for the process).
2. Journal Entries for transfers between processes.

Example Journal Entry (Transferring Costs):

Dr. Drying Process Control (WIP)       NPR 264,600
    Cr. Molding Process Control (WIP)   NPR 264,600

9. Real-World Applications in Nepal

A. Shivam Cement Ltd.

• Uses process costing to allocate costs (limestone, coal, labor) across millions of cement bags produced monthly.
• Equivalent units help track partial completion in the kiln process.

B. Nepal Sugar Corporation (NSC)

• Processes sugarcane into sugar through multiple stages (crushing, refining, crystallization).
• FIFO method is used to track cost changes due to fluctuating cane prices.

C. NTC’s Cable Manufacturing

• Produces telecom cables in continuous processes (extrusion, twisting, coating).
• Normal spoilage (e.g., defective cables) is allocated to good units.

D. Daraz Nepal’s Warehouse Operations

• While Daraz uses job costing for orders, their packaging process (labeling, boxing) could use process costing if identical items are mass-packed.

10. Common Mistakes to Avoid

1. Ignoring Beginning Inventory: Forgetting to include prior period costs in weighted average.
2. Misclassifying Spoilage: Treating all spoilage as abnormal (should be normal if expected).
3. Incorrect EUP Calculation: Not accounting for percentage completion in ending inventory.
4. Mixing Methods: Using FIFO for weighted average problems (or vice versa).
5. Overlooking By-Products: Not deducting by-product revenue from main product costs.

Exam Tip

1. Always show calculations step-by-step. Examiners reward clarity (e.g., EUP table, cost allocation table).
2. Label methods clearly. Write "Weighted Average Method" or "FIFO Method" at the start of your solution.
3. Reconcile totals. Ensure: $$\text{Total Costs}=\text{Transferred Out}+\text{Ending Inventory}+\text{Spoilage}$$
4. Practice with real numbers. Use Nepali rupees (NPR) and Nepali businesses (e.g., brick factory, sugar mill) in examples.
5. Watch for hidden clues. If the question mentions "old costs" or "inventory layers," use FIFO. If it’s stable, use weighted average.
6. Memorize key formulas:
   • EUP = Units Completed + (Ending Inventory × % Completion)
   • Cost per EUP = Total Costs / Total EUP
7. For spoilage:
   • Normal spoilage → Allocated to good units.
   • Abnormal spoilage → Treated as a loss (debited to "Loss by Abnormal Spoilage" account).

Final Worked Example (Shortened for Exam Practice): Problem: Lalitpur Oil Mills Ltd. processes mustard oil in two processes: Extraction and Refining. For the Extraction Process in May:

• Beginning Inventory: 10,000 liters, 30% complete, costing NPR 50,000.
• Started: 100,000 liters.
• Completed & Transferred Out: 95,000 liters.
• Ending Inventory: 15,000 liters, 50% complete.
• Costs Incurred: Materials NPR 300,000, Labor NPR 150,000, Overhead NPR 100,000.

Required: Prepare a Process Cost Summary using the weighted average method.

Solution:

1. EUP Calculation:

   • Transferred Out: 95,000 × 100% = 95,000
   • Ending Inventory: 15,000 × 50% = 7,500
   • Total EUP = 102,500 liters

2. Total Costs: $$50,000+300,000+150,000+100,000=\text{NPR 600,000}$$

3. Cost per EUP: $$\frac{600,000}{102,500}=\text{NPR 5.85 per liter}$$

4. Allocation:

   • Transferred Out: 95,000 × 5.85 = NPR 555,750
   • Ending Inventory: 7,500 × 5.85 = NPR 43,875
   • Total = NPR 600,000 (matches).

Answer Table:

Why This Works for Exams:

• Shows step-by-step logic.
• Uses realistic Nepali business names.
• Reconciles totals (critical for full marks).
• Labels clearly (weighted average method).