Fixed assets amortization rate algorithm

A, the sum of the years method Annual depreciation = (original value - salvage value) / the number of years Second, the sum of the years method Annual depreciation = (original value - salvage value) * the number of years / the total number of years, such as 5 years, the total number of years 1 + 2 + 3 + 4 + 5 = 15, the first year of the depreciation rate of 5/15, the second year for the 4/15, and so on decreasing Third, double declining depreciation Depreciation = 2 / the number of years Annual depreciation = the residual value * depreciation rate Last Two years of depreciation = (residual value - salvage value) / 2 such as 5 years, the depreciation rate = 2/5 = 0.4 If the original value of 10, salvage value of 0.1 The first year: 10 * 0.4 = 4 The second year (10-4) * 0.4 = 2.4 The third year (10-4-2.4) * 0.4 = 1.44 The last two years (10-4-2.4-1.44-1)/2 = 0.58