Depreciation exists because a $50,000 piece of equipment isn't really a $50,000 expense in the single year it's purchased, it's a resource that produces value over several years, and accounting rules require spreading that cost across the years it's actually used rather than distorting one year's profit with the full purchase price.
Straight-line depreciation, the simplest method
Straight-line depreciation = (cost − salvage value) ÷ useful life in years. A $50,000 machine with a $5,000 expected salvage value and a 9-year useful life depreciates by ($50,000 − $5,000) ÷ 9 = $5,000 a year, the same amount every year until it reaches salvage value. It's the most widely used method because it's simple, predictable, and matches assets that lose value at a roughly steady rate. The Depreciation Calculator runs straight-line and other common methods side by side from the same asset details.
Accelerated methods: declining balance and others
Declining-balance methods apply a fixed percentage to the asset's remaining book value each year rather than to the original cost, which produces larger deductions early and progressively smaller ones later, matching assets like vehicles or technology that genuinely lose most of their value in the first few years of use. Double-declining balance, a common variant, applies twice the straight-line rate to the declining book value, then often switches to straight-line for the remaining years once that produces a larger deduction, a detail that trips up manual calculations more than any other part of the process.
The choice of method changes when deductions happen, not how much total depreciation an asset generates over its full useful life, both straight-line and declining-balance methods eventually depreciate the asset down to the same salvage value, they just take different paths to get there, which matters for tax planning and reported profit in any individual year.
Why the method choice matters for cash flow and taxes
Accelerated methods create larger deductions in the earlier years of an asset's life, which lowers taxable income (and therefore tax owed) sooner, a genuine cash-flow advantage even though the total tax paid over the asset's full life is often similar either way, just shifted in timing. Businesses investing heavily in equipment often prefer accelerated depreciation specifically for this timing benefit, while businesses that want smoother, more predictable expense reporting on financial statements often prefer straight-line for its simplicity and consistency year to year.