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How do manufacturing costs flow through direct materials, direct labour and overhead to a cost of goods manufactured and then cost of sales?

Trace manufacturing costs through prime cost and conversion cost, calculate the cost of goods manufactured using work in process, and link it to cost of sales for a manufacturer

WACE Year 12 Accounting and Finance Unit 4 on manufacturing cost flows: direct materials, direct labour and overhead, prime cost and conversion cost, the cost of goods manufactured schedule with work in process, and the link to cost of sales.

Generated by Claude Opus 4.87 min answerUpdated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this dot point is asking
The three manufacturing costs
Prime cost and conversion cost
Cost of goods manufactured
Three inventory stages, two adjustments

What this dot point is asking

SCSA wants you to classify manufacturing costs, calculate prime and conversion cost, and build the cost of goods manufactured and cost of sales figures using inventory movements.

The three manufacturing costs

Prime cost and conversion cost

Cost of goods manufactured

Production is rarely finished exactly at year end, so partly complete units sit in work in process. Cost of goods manufactured adjusts total manufacturing cost for the change in work in process:

\text{COGM} = \text{Total manufacturing cost} + \text{Opening WIP} - \text{Closing WIP}

Then cost of sales adjusts cost of goods manufactured for the change in finished goods:

\text{Cost of sales} = \text{COGM} + \text{Opening finished goods} - \text{Closing finished goods}

Three inventory stages, two adjustments

A manufacturer carries inventory at three stages, and this is what makes its cost flow more involved than a retailer's. Raw materials inventory holds materials bought but not yet used; the materials used figure is opening raw materials plus purchases less closing raw materials. Work in process holds partly finished units; adjusting for its opening and closing balances converts total manufacturing cost into cost of goods manufactured. Finished goods holds completed but unsold units; adjusting for its opening and closing balances converts cost of goods manufactured into cost of sales. The logic of every adjustment is the same: add what was on hand at the start (it will be finished or sold this period) and subtract what is left at the end (it carries forward as a current asset). Tracing costs through these three stages, with the two work-in-process and finished-goods adjustments, is the heart of the manufacturing statement, and only the cost attached to units actually sold ends up as an expense in the Income Statement.

From raw costs to cost of sales

Vela Manufacturing reports direct materials used $120 000, direct labour$ 90 000 and manufacturing overhead $60 000. Opening work in process was$ 15 000 and closing work in process $20 000. Opening finished goods were$ 30 000 and closing finished goods $25 000.

Step 1: Calculate total manufacturing cost, prime cost and conversion cost

Total manufacturing cost is the sum of the three inputs added to production during the period. Prime cost and conversion cost are two useful sub-totals that help managers understand where manufacturing costs are concentrated: prime cost highlights the direct costs of each unit, while conversion cost highlights the cost of transforming materials into finished goods.

\text{Total manufacturing cost} = 120\,000 + 90\,000 + 60\,000 = 270\,000

\text{Prime cost} = 120\,000 + 90\,000 = 210\,000

\text{Conversion cost} = 90\,000 + 60\,000 = 150\,000

Step 2: Calculate cost of goods manufactured

Not all manufacturing cost becomes finished goods within the period: some units are still only partly complete at year end. Cost of goods manufactured therefore adjusts total manufacturing cost for the change in work in process. Adding opening WIP brings in costs carried from last period; subtracting closing WIP defers costs that belong to next period's output.

270\,000 + 15\,000 - 20\,000 = 265\,000 \text{ cost of goods manufactured}

Step 3: Calculate cost of sales

Cost of goods manufactured measures units completed, but some completed units may still be sitting in the finished goods warehouse at year end. Cost of sales adjusts for this by adding opening finished goods (completed last period, sold this period) and subtracting closing finished goods (completed this period, not yet sold).

265\,000 + 30\,000 - 25\,000 = 270\,000 \text{ cost of sales}

Step 4: Verify what reaches the Income Statement

Only the cost attached to goods actually sold flows to the Income Statement as cost of sales. The closing inventories of $20 000 work in process and$ 25 000 finished goods are carried forward as current assets on the Balance Sheet, matching costs to the future period in which those goods will be sold.

Final answer: Total manufacturing cost is $270 000 (prime cost$ 210 000, conversion cost $150 000), cost of goods manufactured is$ 265 000, and cost of sales is $270 000.

Exam-style practice questions

Practice questions written in the style of SCSA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

WACE 20228 marksTarn Manufacturing reports direct materials used

140 000, direct labour

100 000 and manufacturing overhead

70 000. Opening work in process

18 000, closing work in process

26 000. Opening finished goods

35 000, closing finished goods $28 000. Calculate prime cost, conversion cost, cost of goods manufactured and cost of sales.

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An 8 mark response needs all four figures with correct adjustments.

Prime cost. Direct materials plus direct labour $= 140\,000 + 100\,000 = 240\,000$ .

Conversion cost. Direct labour plus overhead $= 100\,000 + 70\,000 = 170\,000$ .

Total manufacturing cost. $140\,000 + 100\,000 + 70\,000 = 310\,000$ .

Cost of goods manufactured. $310\,000 + 18\,000 - 26\,000 = 302\,000$ (add opening WIP, subtract closing WIP).

Cost of sales. $302\,000 + 35\,000 - 28\,000 = 309\,000$ (add opening finished goods, subtract closing finished goods). Markers reward the prime and conversion groupings, the WIP adjustment for COGM, and the finished goods adjustment for cost of sales.

WACE 20235 marksExplain the difference between cost of goods manufactured and cost of sales, and explain why direct labour is included in both prime cost and conversion cost.

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A 5 mark response needs both distinctions.

COGM versus cost of sales. Cost of goods manufactured is the cost of units completed during the period, found by adjusting total manufacturing cost for the change in work in process. Cost of sales is the cost of units actually sold, found by adjusting cost of goods manufactured for the change in finished goods inventory. They differ whenever finished goods stock changes; only cost of sales reaches the Income Statement as an expense.

Direct labour in both. Prime cost is direct materials plus direct labour, the costs most directly tied to each unit. Conversion cost is direct labour plus overhead, the cost of converting materials into finished goods. Direct labour belongs to both because it is both a direct cost of the unit and part of the conversion effort. Markers reward the completed-versus-sold distinction and the dual role of direct labour.