Straight line depreciation is a method used to calculate the periodic reduction of an asset’s book value over its useful life. This approach assumes that the cost to acquire the asset, minus any residual value, will be evenly spread out across the years of its usage. The calculation is made by taking the difference between the cost and salvage value of the asset divided by its estimated useful life. Businesses may also choose to make journal entries for straight line depreciation to better track changes in their financial statements throughout the year. By making these journal entries, businesses can accurately reflect the true costs associated with their assets over time.