Units of Production Depreciation

The units of production method is a depreciation approach where the expense recorded is directly tied to the actual usage of an asset — measured in units produced, hours operated, or output generated — rather than the passage of time. It is most appropriate when wear and tear, rather than obsolescence, drives an asset's decline in value.

The formula has two steps. First, calculate the depreciation per unit: (Asset Cost − Salvage Value) ÷ Estimated Total Units Over Lifetime. Then multiply by actual units produced in the period: Depreciation Expense = Depreciation per Unit × Units Produced This Period.

Straight-line depreciation spreads the cost evenly across the useful life regardless of how much the asset is used. Units of production depreciation is variable — in periods of high production, the expense is higher, and in idle periods it may be near zero. This makes it a more accurate reflection of actual wear and tear.

This method is ideal for manufacturing equipment, mining assets, oil fields, or vehicles where depreciation is driven by usage rather than time. It is especially useful when production levels fluctuate significantly from period to period, since the depreciation charge mirrors actual asset consumption.

Salvage value (also called residual value) is the estimated worth of the asset at the end of its useful life. It is subtracted from the asset cost to determine the depreciable base — the total amount that will be depreciated over the asset's lifetime. A higher salvage value reduces the total depreciation recognized.

The main limitation is that it requires a reliable estimate of the asset's total lifetime output, which can be difficult to determine. If actual usage significantly exceeds or falls short of the estimate, the depreciation schedule may become inaccurate. It also requires more detailed record-keeping of actual production figures each period.

In the United States, the IRS generally requires MACRS (Modified Accelerated Cost Recovery System) for tax depreciation of most assets. The units of production method is primarily used for financial reporting (GAAP) purposes, where it is permitted under both US GAAP and IFRS for assets whose usage can be reliably measured.

Once accumulated depreciation equals the depreciable base (Asset Cost − Salvage Value), no further depreciation is recorded, even if the asset continues to be used. The asset remains on the books at its salvage value until it is disposed of or retired.