What Is Work in Process Inventory?
Work in process (WIP) inventory, sometimes called work in progress, is the value of partially completed goods that are still moving through the production process, no longer raw material but not yet finished product ready for sale. It sits between raw materials inventory and finished goods inventory on the balance sheet, representing everything currently in the middle of being built.
What Is Included in WIP Value
- Direct materials consumed so far:
Raw materials that have already been incorporated into the partially built product.
- Direct labor incurred so far:
Wages for work already performed on the unit up to its current stage of completion.
- Allocated manufacturing overhead:
A proportional share of factory overhead applied based on the work completed to date.
This is the same three-component structure used in job costing, direct materials, direct labor, and allocated overhead, applied to a product that is only partway through production rather than fully complete.
Calculating WIP Value
FORMULA
Ending WIP = Beginning WIP + Manufacturing Costs Incurred During the Period − Cost of Goods Completed and Transferred to Finished Goods
EXAMPLE
A manufacturer starts the month with $85,000 in WIP, incurs $340,000 in direct materials, labor, and overhead during the month, and completes and transfers $310,000 worth of finished units to finished goods inventory.
Ending WIP = $85,000 + $340,000 − $310,000 = $115,000.
That $115,000 represents units still on the production floor at various stages of completion at month end.
WIP Inventory vs. Finished Goods vs. Raw Materials
- Raw materials:
Purchased inputs that have not yet entered production.
- Work in process:
Materials that have entered production and had some labor and overhead applied, but are not yet complete.
- Finished goods:
Fully completed units ready for sale, with all production cost fully incorporated.
Inventory moves through these three stages in sequence, and the total value of all three, plus any inventory in transit, is what appears as total inventory on the balance sheet.
Why WIP Is Difficult to Value Precisely
Unlike raw materials or finished goods, which have a clear, discrete value, WIP by definition represents units at every possible stage of partial completion simultaneously, some nearly done, some barely started. Estimating the percentage of completion for units still in process, and therefore how much labor and overhead to allocate to them, requires judgment that finished units and untouched raw materials do not.
This is the same percentage-of-completion estimation challenge described in progress billing, applied to internal production cost rather than external customer billing. Businesses commonly use standard costing to simplify this, applying predetermined cost rates by production stage rather than calculating exact actual cost for every unit in process at any given moment.
Why WIP Accuracy Matters for Job Costing
For businesses running job costing, described in job costing, WIP value for a specific job is the real-time answer to how much has been invested in that job so far, before it is complete and before final profitability can be assessed. If material and labor costs are not coded to the correct job promptly as they are incurred, WIP for that job understates true cost, making a job look more profitable mid-stream than it actually is, right up until the missing costs eventually post and correct the picture, often after decisions have already been made based on the wrong number.
Frequently Asked Questions About Work in Process Inventory
1. What is work in process inventory?
Work in process (WIP) inventory is the value of partially completed goods still moving through production, no longer raw material but not yet finished goods ready for sale, including the materials, labor, and overhead already incurred on those units.
2. How do you calculate work in process inventory?
Ending WIP equals beginning WIP plus manufacturing costs incurred during the period, minus the cost of goods completed and transferred to finished goods. A business starting with $85,000 in WIP, incurring $340,000 in costs, and completing $310,000 worth of units ends with $115,000 in WIP.
3. What is the difference between raw materials, WIP, and finished goods?
Raw materials are purchased inputs not yet in production. WIP is materials that have entered production with some labor and overhead applied but are not yet complete. Finished goods are fully completed units ready for sale.
4. Why is WIP inventory hard to value precisely?
It represents units at every stage of partial completion simultaneously, requiring an estimate of percentage complete and how much labor and overhead to allocate to units still in process, a judgment call that finished units and untouched raw materials do not require.
5. How does WIP relate to job costing?
For job-costed work, WIP value for a specific job shows real-time investment in that job before it is complete. If costs are not coded to the job promptly, WIP understates true cost, making the job look more profitable than it actually is until the missing costs eventually post.
6. Is work in process the same as work in progress?
Yes, the two terms are used interchangeably to refer to the same concept: partially completed production inventory. Work in process is more common in manufacturing accounting; work in progress is used more broadly, including in construction and project contexts.
