Hong Life CalculatorsUnderstanding the straight-line depreciation calculator — concept and principle
Straight-line depreciation spreads the cost of a long-lived asset, such as a machine, vehicle or computer, evenly over its useful life. This calculator gives the annual depreciation charge, the depreciation accumulated so far, and the asset's current book value. Small business owners, accountants and students use it for bookkeeping, budgeting and checking financial statements. It works with any currency.
How it is calculated
- Annual depreciation = (asset cost − salvage value) ÷ useful life (years)
- Accumulated depreciation = annual depreciation × age, capped at cost − salvage
- Book value now = cost − accumulated depreciation, never below salvage value
Salvage (residual) value is what you expect the asset to be worth at the end of its useful life. Age is how many years the asset has been in use.
The principle
Accounting matches costs to the periods that benefit from them. An asset that helps earn revenue for five years should not be charged as an expense all in the year it was bought. Straight-line assumes the asset delivers equal benefit each year, so the depreciable amount (cost minus salvage) is divided equally. Book value therefore falls along a straight line from cost to salvage value, which gives the method its name. Accounting standards such as IAS 16 accept it when the pattern of use is roughly even; other methods, like declining balance, front-load the charge.
Worked example
- Cost = 50,000 USD, salvage = 5,000 USD, life = 5 years, age = 2 years.
- Annual depreciation = (50,000 − 5,000) ÷ 5 = 9,000.00 USD.
- Accumulated = 9,000 × 2 = 18,000.00 USD.
- Book value = 50,000 − 18,000 = 32,000.00 USD.
- At the end of year 5, accumulated depreciation reaches 45,000 and book value equals the 5,000 salvage value.
How to read the result
Annual depreciation is the expense recorded each year; here it is 18% of the original cost. Book value is an accounting figure, not market value: the asset might sell for more or less. If the asset is used beyond its estimated life, the calculator keeps book value at salvage and stops adding depreciation, as in practice.
Common mistakes
- Forgetting to subtract salvage value before dividing.
- Taking a full year of depreciation in the year of purchase when the asset was bought mid-year (many businesses pro-rate by months).
- Confusing book value with resale value.
- Assuming tax depreciation rules are the same as accounting rules.
Frequently asked questions
Can salvage value be zero?
Yes. Then the whole cost is depreciated and book value reaches zero at the end of the useful life.
Is land depreciated?
Generally no. Land is usually treated as having an unlimited useful life, so only buildings and equipment are depreciated.
When should I use declining balance instead?
When an asset loses most of its value or usefulness in its early years, such as some vehicles and electronics, a declining-balance method can match reality better.
Sources: IFRS Foundation, IAS 16 Property, Plant and Equipment