How To Calculate Depreciation

Depreciation is the accounting process of spreading the cost of a long-lived asset across the years that benefit from it. Instead of recording the whole purchase in one year, the expense is recognised gradually.

The depreciable base is the asset cost minus the expected salvage value. It is the amount that will actually be written off over the asset's life, because the salvage value is expected to be recovered when the asset is sold or scrapped.

The useful life is the number of years the asset is expected to be productive. It is an estimate, informed by the manufacturer's guidance, industry practice and the way the asset will be used.

Straight-line depreciation divides the base evenly across the life, giving the same expense every year. It is the default method because it is simple, transparent and easy to reconcile against the asset register.

The annual expense is the depreciable base divided by the useful life. On a twenty-two thousand dollar base over eight years that is two thousand seven hundred and fifty a year.

The monthly expense is the annual figure divided by twelve. It is useful when the accounts are prepared monthly and when the depreciation is allocated to a cost centre.

The asset's book value falls by the annual depreciation each year. After the full life it reaches the salvage value, at which point depreciation stops unless the estimate is revised.

Declining-balance methods front-load the expense, applying a fixed percentage to the remaining book value each year. They suit assets that lose value quickly in the early years, such as vehicles and technology.

Units-of-production methods tie the expense to usage rather than time, which suits machinery whose wear depends on output. The total written off is the same, but the timing follows activity.

The choice of method affects reported profit and the tax bill in each year, but not the total written off over the life. Tax rules in most jurisdictions specify which methods are allowed for the deduction.

Improvements that extend an asset's life or increase its capacity are usually capitalised and depreciated over the remaining life, while repairs that simply maintain it are expensed as incurred.

Disposing of the asset before the end of its life produces a gain or loss equal to the difference between the sale proceeds and the book value at that point, which is why tracking the book value matters.

The residual value at the end of the life is an estimate made at the start, and it is rarely exactly right. When an asset is sold for more or less than the remaining book value, the difference is recorded as a gain or a loss on disposal, which is why keeping the register up to date matters.

Grouping similar assets together simplifies the register without changing the total. A pool of identical laptops purchased in the same month can be depreciated as one line, which reduces administration and makes the annual charge easier to audit.

The calculator models the figures entered and nothing more. It uses the straight-line method only and does not know the tax rules that apply. Treat the output as a management-accounting figure and confirm the tax treatment separately.