Process costing is a method of cost accounting where total production costs (materials, labour and overhead) are accumulated for each stage of a manufacturing process and then divided by the number of units produced in that period to arrive at a cost per unit.
It is used when a business makes large volumes of identical or near-identical products in a continuous flow, such as chemicals, cement, textiles or beverages. Unlike job costing, which tracks costs for individual orders, process costing assumes that every unit passing through a process is identical and should bear an equal share of the costs incurred.
What are the key concepts you need to understand first
Before calculating process costs, three concepts must be clear:
Equivalent units of production
Not all units in a batch are complete at the end of a period. Some are partially processed, called work in progress (WIP). To account for these fairly, WIP is converted into equivalent units: a unit that is 50% complete counts as 0.5 finished units. This prevents the cost of partially finished goods from being spread over fully finished units.
Normal and abnormal losses
In many manufacturing processes, some loss of material is expected (evaporation, trimming, spoilage). This is called normal loss and its cost is absorbed into the cost of good output. Loss beyond what is expected is an abnormal loss, recorded separately as an expense.
Abnormal gains
This arises when the actual loss in production is less than the expected normal loss. It usually reflects higher operational efficiency, improved production methods or better-performing machinery. Such gains indicate effective resource utilisation and are treated separately in process costing to measure the improvement in production performance accurately.
Scrap Value
In some manufacturing processes, the material lost during production can still generate a minor recovery value. For instance, metal scraps produced while manufacturing screws may be collected and sold to scrap dealers, helping businesses recover a small portion of the production cost.
When to use process costing
Process costing is suited to manufacturing environments with specific characteristics. Before adopting it, check that your production meets these conditions:
- Every unit produced is identical, or near-identical, to every other unit (for example, bags of flour or bottles of paint).
- The manufacturing line runs without stopping to complete one job before starting another.
- Raw materials and labour go into a batch or process, not a specific item.
- Output is measurable in standard units such as litres, kilograms, metres or pieces.
Industries in India where process costing is standard include sugar mills, steel plants, paper manufacturers, soap and detergent makers and pharmaceutical bulk drug production.
If your output varies by specification, customer or design from one order to the next, job costing is more appropriate.
How to calculate process cost per unit
The calculation follows a fixed sequence. The example below uses the weighted average method for a cement plant with two processes (grinding and blending) in a given month:
Step 1: Determine units to account for
Add opening WIP (units partially complete from last period) to units started in the current period. This total must equal completed units transferred out plus closing WIP.
Step 2: Calculate equivalent units
Multiply closing WIP units by their percentage of completion. For example, if 500 units are in closing WIP at 60% completion for materials and 40% for conversion costs, equivalent units are 300 for materials and 200 for conversion costs. Add these to completed units to get total equivalent units.
Step 3: Compute total costs to account for
Add the cost of opening WIP (under weighted average, this is included in the pool) to all costs added during the period: direct materials, direct labour and manufacturing overhead.
Step 4: Calculate cost per equivalent unit
Divide total costs by total equivalent units, separately for materials and conversion costs. These two figures, added together, give the cost per equivalent unit.
Step 5: Assign costs to output and WIP
Multiply cost per equivalent unit by units completed (for transferred-out cost) and by closing WIP equivalent units (for ending WIP cost). The two figures must sum to the total costs from Step 3.
Conclusion
Process costing gives manufacturers a structured way to price their output accurately when individual unit tracking is not practical. Getting the equivalent unit calculation right and consistently distinguishing normal from abnormal losses are the two areas that have the most impact on the reliability of the final cost figure.
For businesses managing multiple processes, departments or production runs, TallyPrime supports process costing workflows so costs flow correctly from raw material intake through each production stage to finished goods valuation.
