Comparing depreciation methods
The method chosen changes only the timing of the depreciation expense, not the total amount depreciated over the asset's life — all three methods depreciate the same (cost − salvage) depreciable base by the end of the useful life.
| Method | Year 1 pattern | Best suited for |
|---|---|---|
| Straight-line | Equal expense every year | Assets that lose value evenly over time, e.g. office furniture |
| Double-declining balance | Largest expense in year 1, declining each year | Assets that lose most value early, e.g. vehicles, computers |
| Sum-of-the-years'-digits | Accelerated, but smoother than DDB | Assets with moderate early wear and tear |
- This calculator is a book/financial-statement depreciation illustration; it does not compute tax depreciation under the IRS MACRS system (IRS Publication 946), which uses fixed statutory percentages and conventions rather than any of these three methods directly.
- The double-declining balance calculation floors the annual charge at the salvage value, so book value never depreciates below the estimated residual worth of the asset.
What is depreciation?
Depreciation is the systematic allocation of a fixed asset's cost, less its expected salvage value, over the periods that benefit from using it. Under US GAAP (FASB Accounting Standards Codification Topic 360, Property, Plant, and Equipment), depreciation matches an asset's cost to the revenue it helps generate rather than expensing the full cost at purchase, and it is an accounting allocation rather than a measure of the asset's actual market value at a given date.
The three methods this calculator computes allocate the same total depreciable base (cost minus salvage value) differently over time. Straight-line depreciation spreads the base evenly across the useful life. Double-declining balance (DDB) and sum-of-the-years'-digits (SYD) are both accelerated methods that front-load more expense into the early years, with DDB typically the more aggressive of the two.
This calculator illustrates standard book (financial-statement) depreciation. For US federal income tax purposes, the IRS generally requires the Modified Accelerated Cost Recovery System (MACRS), described in IRS Publication 946, which uses fixed statutory recovery periods and percentage tables rather than any of the three methods shown here — tax depreciation and book depreciation are commonly calculated separately.
How to use this depreciation calculator
- Enter the asset's original cost, including the purchase price and any costs to place it into service.
- Enter the estimated salvage (residual) value expected at the end of the asset's useful life.
- Enter the useful life of the asset in years.
- Select a depreciation method: straight-line, double-declining balance, or sum-of-the-years'-digits.
- Read the Year 1 and Year 2 depreciation expense, the total depreciable base, and the straight-line annual figure shown for comparison.
The formula behind each depreciation method
All three methods start from the same depreciable base: asset cost minus salvage value. Straight-line depreciation divides that base evenly by the useful life. Double-declining balance applies a fixed rate (2 ÷ useful life) to the asset's remaining book value each year, producing a shrinking expense that this calculator floors so book value never falls below the salvage estimate. Sum-of-the-years'-digits weights each year's share of the depreciable base by its remaining useful life divided by the sum of the years' digits.
For example, a $50,000 asset with a $5,000 salvage value and a 5-year life has a $45,000 depreciable base. Straight-line depreciation is $9,000 per year. Double-declining balance charges 40% of cost in year 1 ($20,000). Sum-of-the-years'-digits charges 5/15 of the base in year 1 ($15,000).
Common mistakes
- Assuming an accelerated method (DDB or SYD) changes the total lifetime depreciation — it only changes the timing; the total always equals cost minus salvage.
- Entering a salvage value equal to or greater than the asset cost, which leaves no depreciable base.
- Confusing book depreciation methods with IRS tax depreciation (MACRS), which follows fixed statutory recovery tables under Publication 946 rather than straight-line, DDB, or SYD directly.
- Applying double-declining balance without capping it at salvage value, which can depreciate an asset below its expected residual worth.
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What's the difference between straight-line and accelerated depreciation?
Straight-line depreciation charges an equal expense every year of the asset's useful life. Accelerated methods, such as double-declining balance and sum-of-the-years'-digits, charge more depreciation in the early years and less later, though both reach the same total depreciation (cost minus salvage) by the end of the useful life.
Does the depreciation method affect total depreciation over an asset's life?
No. All three methods — straight-line, double-declining balance, and sum-of-the-years'-digits — depreciate the same total depreciable base (cost minus salvage value) over the asset's useful life; only the year-by-year timing of the expense differs.
What is salvage value?
Salvage value, also called residual value, is the estimated amount an asset could be sold for at the end of its useful life. It reduces the depreciable base, since accounting depreciation only allocates the portion of cost expected to be consumed by use, not the full purchase price.
Which depreciation method does the IRS require for tax purposes?
Neither method shown here directly. US federal tax depreciation generally follows the Modified Accelerated Cost Recovery System (MACRS) described in IRS Publication 946, which applies fixed statutory recovery periods and percentage tables that differ from straight-line, double-declining balance, and sum-of-the-years'-digits book depreciation.
Can salvage value be zero?
Yes. Many assets are depreciated to a zero salvage value, particularly when the asset is expected to have no meaningful resale or scrap value at the end of its useful life. Entering zero simply makes the depreciable base equal to the full asset cost.
Kaynaklar
- Financial Accounting Standards Board (FASB). Accounting Standards Codification, Topic 360, Property, Plant, and Equipment. fasb.org.
- Internal Revenue Service. Publication 946, How To Depreciate Property. irs.gov.
- U.S. Small Business Administration. Understanding financial statements. sba.gov.
- Kieso DE, Weygandt JJ, Warfield TD. Intermediate Accounting. Wiley.