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Depreciation Calculator

Computes an asset's depreciation expense for a chosen year, the accumulated depreciation and the book value, plus the full year-by-year schedule, using the straight-line, 150 % declining-balance, double-declining-balance or sum-of-the-years'-digits method.

When to use

You need book (financial-statement) depreciation of equipment, vehicles or buildings over their useful life, or want to compare accelerated methods with straight-line.

Do not use when: You need US tax depreciation under MACRS with its conventions and class lives (IRS Publication 946 tables), or units-of-production depreciation.

Formula

base = cost − salvage. Straight-line: D_y = base / life. Declining balance: D_y = max(book_{y−1} × f/life, (book_{y−1} − salvage)/(life − y + 1)) with f = 1.5 or 2, never below salvage. Sum-of-years-digits: D_y = base × (life − y + 1) / (life × (life + 1) / 2).

Full-year convention (the asset is placed in service at the start of year 1). Declining-balance methods switch to straight-line over the remaining life when that gives a larger deduction, as in IRS Publication 946, which also guarantees the book value ends exactly at salvage.

Inputs

Parameter	Type	Unit	Required	Description
`cost`	number		yes	Purchase price plus costs to put the asset in service. Range: > 0, ≤ 1000000000000
`salvage_value`	number		default 0	Estimated value at the end of the useful life; must be below cost. Range: ≥ 0, ≤ 1000000000000
`useful_life_years`	integer	years	yes	Years over which the asset is depreciated. Range: ≥ 1, ≤ 40
`method`	enum: straight_line \| declining_balance \| double_declining \| sum_of_years_digits		default straight_line	Depreciation method.
`year`	integer		default 1	Year of the asset's life to report (1 = first year). Range: ≥ 1, ≤ 40

Outputs

Output	Type	Unit	Description
`depreciation_for_year`	number		Expense recognised in the requested year.
`accumulated_depreciation`	number		Total depreciation through the end of that year.
`book_value_end_of_year`	number		cost − accumulated_depreciation.
`depreciable_base`	number		cost − salvage_value.
`annual_rate_percent`	number	%	Straight-line 100/life of the base; declining balance 150/life or 200/life of the opening book value; SYD the year's fraction of the base.
`method_used`	string		Name of the method applied.
`schedule`	list		One row per year: year, depreciation, accumulated, book_value (at most 40 rows).

Example

10,000 cost, 1,000 salvage, 5 years, straight-line, year 3: {"cost":10000,"salvage_value":1000,"useful_life_years":5,"method":"straight_line","year":3} → {"depreciation_for_year":1800,"accumulated_depreciation":5400,"book_value_end_of_year":4600,"depreciable_base":9000,"annual_rate_percent":20,"method_used":"Straight-line"}

10,000 cost, 1,000 salvage, 5 years, double-declining, year 2: {"cost":10000,"salvage_value":1000,"useful_life_years":5,"method":"double_declining","year":2} → {"depreciation_for_year":2400,"accumulated_depreciation":6400,"book_value_end_of_year":3600,"annual_rate_percent":40,"schedule":[{"year":1,"depreciation":4000,"accumulated":4000,"book_value":6000},{"year":2,"depreciation":2400,"accumulated":6400,"book_value":3600},{"year":3,"depreciation":1440,"accumulated":7840,"book_value":2160},{"year":4,"depreciation":864,"accumulated":8704,"book_value":1296},{"year":5,"depreciation":296,"accumulated":9000,"book_value":1000}]}

GET https://tttkmbb.com/api/v1/calculate/depreciation?cost=10000&salvage_value=1000&useful_life_years=5&method=straight_line&year=3

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/depreciation (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/depreciation · Markdown: https://tttkmbb.com/finance/depreciation.md · JSON definition: https://tttkmbb.com/finance/depreciation.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="depreciation"
OpenAPI operationId: calculate_depreciation
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

IRS Publication 946 – How To Depreciate Property (government)
Investopedia – Double-Declining Balance (DDB) Depreciation Method (reference)
Wikipedia – Depreciation (reference)

FAQ

Why does double-declining balance stop early?

It applies a fixed rate to a shrinking book value and never depreciates below salvage, so the final years are capped (296 in year 5 of the example) or switch to straight-line.

Which method should I use?

Straight-line is the default for financial statements; accelerated methods front-load expense for assets that lose value quickly. Tax depreciation follows separate rules (MACRS in the US).

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