Depreciation in accounting is used to spread an asset’s cost over the number of years it will be useful to the entity. It is used to reflect the decreasing value of the asset over time due to wear-and-tear, usage, technological outdating, etc… The original purchase affects the entity’s cash account one time. For the remaining useful life of the item, the assets are affected on the balance sheet as accumulated depreciation and the expenses are affected on the income statement as depreciation expenses. Depreciation is a way to spread the expense of an asset over the span of its useful life, as long as that span is longer than one accounting period. Many different types of assets are depreciable including tangible assets (buildings, equipment, machinery) and intangible assets (software, patents, copyrights). There are several types of depreciation methods used in bookkeeping today. A few are outlined below.
Straight-line depreciation method is graphically exactly what the name implies. It is a straight, horizontal line on a graph of annual depreciation expense versus years of life. It is one pre-determined standard amount that is divided over the estimated useful life span of the asset. This expense is then recorded once per year for the appropriate length of time. This can be calculated by taking the difference of the original cost minus the salvage value (or the amount that the item can be sold for at the end of its useful life to the entity) divided by the useful life. This calculation will give you the amount to be recorded as depreciation each year. For example, if an asset is purchased for $125,000, it’s salvage value is $5,000 ($125,000 – $5,000 = $120,000), and it is estimated to last the entity 6 years ($120,000/ 6 years = $20,000/year) an accumulated depreciation of $20,000 should be recorded each year for the next 6 years.
Related to straight-line depreciation is units-of-production depreciation. Instead of spreading the total asset depreciation over a span of time, it is spread over the amount of units it is expected to produce in its useful life. The depreciation is constant for each unit produced, but if some years are more fruitful in production than others, the amount recorded as depreciation will vary. This is most relevant with an asset that has a useful life closely related to its output. For example, if the same asset listed above was estimated to be able to produce 60,000 units of product in its lifetime ($120,000/60,000) each unit produced should be recorded as an accumulated depreciation of $2. If in 2007 the entity was able to produce 12,000 units, $24,000 should be recorded as accumulated depreciation. Likewise if in 2008 the entity was able to produce 16,000 units, an accumulated depreciation of $32,000 should be recorded for that year.