Under the sum-of-the-years-digits method, the calculation is determined based on the number of years. An easy formula to use in determining the denominator is (n<sup>2</sup>+n)/2 where n is equal to the useful life of the asset in years. The numerator is the number of remaining years (including that year). The fraction is applied to the original historical cost less residual value. | Under the sum-of-the-years-digits method, the calculation is determined based on the number of years. An easy formula to use in determining the denominator is (n<sup>2</sup>+n)/2 where n is equal to the useful life of the asset in years. The numerator is the number of remaining years (including that year). The fraction is applied to the original historical cost less residual value. |