There are several different depreciation methods. Straight line depreciation is the most frequently used and most simplest. With this method, you subtract the salvage value of the asset in question from its original cost and divide it by the estimated life of the of the asset. In the double-declining balance method, the depreciation rate used is twice that used in straight line depreciation.
. In MACRS, the assets are categorized and each category has a specified useful life.