Accumulated Depreciation Calculator

How to use and interpret accumulated depreciation

Accumulated depreciation is the total depreciation expense recognized for a tangible fixed asset from the date it is placed in service through the reporting date. It is usually presented as a contra-asset balance that reduces the asset's gross carrying amount. This calculator estimates that cumulative balance and the related net book value. It is designed for planning, internal analysis, and educational use; it does not replace an entity's accounting policy, tax rules, or professional judgment.

Choose the method that matches the asset

Straight line spreads the depreciable basis evenly across useful life. It is often appropriate when the asset provides benefits relatively evenly. A higher cost or lower salvage value increases annual expense, while a longer useful life reduces annual expense. Declining balance applies a fixed rate to opening book value, producing higher expense earlier and lower expense later. Enter the policy rate as a percentage; very high rates accelerate recognition but the calculator still protects the salvage floor.

Sum of the years' digits is another accelerated method. It allocates the largest fraction of depreciable basis to year one and progressively smaller fractions afterward. Units of production links expense to actual use rather than time. Use a consistent unit such as machine hours, miles, cycles, or units manufactured. Estimated lifetime units must be greater than zero, and cumulative units should not exceed the lifetime estimate unless you deliberately want the result capped at the depreciable basis.

Field-by-field guidance

• Cost of the asset: enter the capitalized acquisition cost. Do not include land in a building calculation because land is generally not depreciated. Higher cost increases the depreciable basis and potential accumulated depreciation.
• Salvage value: enter the expected residual amount at the end of useful life. It is optional in the sense that zero is allowed, but it cannot exceed cost. A higher salvage value lowers total depreciable basis.
• Useful life: enter whole years for straight line, declining balance, or sum-of-the-years' digits. A longer life spreads expense over more schedule rows. For declining balance, useful life defines the displayed horizon; the chosen rate determines the expense pattern.
• Years elapsed: enter completed years through the reporting date. The value is capped at useful life. Zero produces no accumulated depreciation and leaves book value equal to cost.
• Annual depreciation rate: used only for declining balance. Enter a positive percentage up to 100%. The rate applies to opening book value, not original cost, so annual expense declines over time.
• Estimated lifetime units and cumulative units produced: used only for units of production. The per-unit expense equals depreciable basis divided by estimated lifetime units. Actual cumulative usage drives accumulated depreciation directly.

Understanding each result

Accumulated depreciation is the cumulative expense recognized to date. A zero balance generally means no depreciation period or usage has been entered. Net book value equals original cost minus accumulated depreciation; it is an accounting carrying amount, not necessarily market value. Depreciable basis equals cost minus salvage value and represents the maximum amount this model can depreciate.

Current-period expense is the expense in the selected year for time-based methods. Under units of production, it shows the cumulative usage-based expense represented by the entered units because no separate current-period units are requested. Cost depreciated compares accumulated depreciation with original cost, while basis depreciated compares it with the amount eligible for depreciation. The latter reaches 100% when the asset is fully depreciated to salvage value.

Formula logic and schedule checks

Straight-line accumulated depreciation = ((cost − salvage value) ÷ useful life) × years elapsed.

Declining balance multiplies each year's opening book value by the rate and caps expense at the amount needed to reach salvage value. Sum-of-the-years' digits multiplies depreciable basis by a decreasing fraction: remaining life divided by the sum of all life-year digits. Units of production multiplies actual cumulative units by depreciation per unit. In every method, accumulated depreciation is capped at depreciable basis and net book value cannot fall below salvage value.

The donut shows how original cost is currently allocated among recognized depreciation, remaining depreciable basis, and residual value. The comparison bars show original cost, accumulated depreciation, and net book value. The schedule lets you cross-check opening value, annual expense, cumulative expense, and closing value. Each row cross-foots: opening book value minus depreciation expense equals closing book value, and original cost minus accumulated depreciation equals closing book value.

Common mistakes and practical limits

Do not confuse depreciation expense for one period with accumulated depreciation for all periods. Do not use market resale estimates as book value without a separate valuation analysis. Review useful life and salvage assumptions when operating conditions materially change. Tax depreciation can differ substantially from financial-statement depreciation, including conventions, recovery periods, bonus depreciation, and asset classes. For U.S. tax context, consult the IRS overview of Publication 946, the current Publication 946, and IRS Topic 704. For a plain-language distinction between annual expense and the contra-asset balance, see Investopedia's accumulated depreciation explanation.