In the straight line method the yearly percentage of cost lost through accured depreciation is found by

Cost of asset less expected residual value / Expected useful life (years

Explanation:

Where the depreciable amount is charged in equal amounts to each reporting period over the expected useful life of the asset, this method of calculating depreciation is known as straight line method.

The yearly percentage of cost lost through accrued depreciation in straight line method is found by following formula:

Cost of asset less expected residual value / Expected useful life (years)