Straight Line Method Formula is a quick and easy way to calculate the depreciation of an asset. It is based on the assumption that the asset’s value decreases evenly over its lifetime, at a linear rate. This means that for every year of use, it loses the same amount of value. To calculate using Straight Line Method Formula, simply divide the cost of the asset less estimated salvage value by the number of years you plan to use it for. This will give you the depreciation expense for each year.