We first consider normal spoilage. The following example illustrates how to count normal spoilage units when computing physical and equivalent output units in a process-costing system.

The details are as follows:
Work in process, beginning inventory (May 1)
Physical units: 0
Started during May
Physical units: 10,000
Good units completed and transferred out during May
Physical units: 5,000
Units spoiled (all normal spoilage)
Physical units: 1,000
Work in process, ending inventory (May 31)
Physical units: 4,000
Direct materials costs added in May
Direct materials: $270,000.
Spoilage is detected upon completion of the process and has zero net disposal value.
An inspection point is the stage of the production process at which products are examined to determine whether they are acceptable or unacceptable units. Spoilage is assumed to occur at the stage of completion where inspection occurs. In our example, spoiled units are 100% complete with respect to direct materials.
Exhibit 19-1 calculates and assigns the cost of direct materials used to produce both good units and normal spoilage units. Overall, Chipmakers generated 10,000 equivalent units of output: 5,000 equivalent units in good units completed 4,000 units in ending work in process and 1,000 equivalent units in normal spoilage Equivalent-unit cost is $27 (total direct materials costs, equivalent units). The total cost of good units completed and transferred out, which includes the cost of normal spoilage, is The ending work in process is

Details of the costs are as follows:
Costs to account for: $270,000
Divide by equivalent units of output: cost to account for divided by 10,000
Cost per equivalent unit of output: $27
Assignment of costs
Good units completed (5,000 units multiplied by $27 per unit): $135,000
Add normal spoilage (1,000 units multiplied by $27 per unit): 27,000
Total costs of good units completed and transferred out: 162,000
Work in process, ending (4,000 units multiplied by $27 per unit): 108,000
Costs accounted for: $270,000.
Notice that the 4,000 units in ending work in process are not assigned any costs of normal spoilage because they have not yet been inspected. Undoubtedly some units in ending work in process will be found to be spoiled after they are completed and inspected in the next accounting period. At that time, their costs will be assigned to the good units completed in that period. Note that Exhibit 19-1 identifies normal spoilage costs of $27,000 to highlight and focus attention on the potential economic benefits of reducing spoilage.