How to use: Calculate asset value decline over time using straight-line depreciation method. Enter Asset Cost (original purchase price), Salvage Value (estimated worth at end of useful life), and Useful Life (years the asset will be productive). Results show: Annual Depreciation (yearly expense deduction), Total Depreciation (cumulative value loss), and Book Value after first year. Useful life is your own estimate of how long you expect to use the asset. This is accounting depreciation. In the UK, tax relief on business assets is usually given through capital allowances instead, so check HMRC guidance or ask an accountant.