Last updated: May 2026
Quick Answer
Straight-line depreciation spreads the cost of an asset evenly across its useful life: (Cost − Salvage Value) ÷ Useful Life. Declining balance depreciates a fixed percentage of the remaining book value each year, front-loading more expense in early years.
Key Takeaways
- ✓ Non-Cash Expense: Depreciation reduces taxable income without any cash leaving your bank account — the cash left when you bought the asset.
- ✓ Salvage Value: Also called residual or scrap value — what you expect to sell the asset for at end of life. Many businesses use $0 for simplicity.
- ✓ Tax ≠ Book: The IRS mandates MACRS schedules for tax returns, which often differ from the straight-line method used in your financial statements.
- ✓ Method affects profit: Accelerated (declining balance) depreciation reduces taxable income more in early years, deferring taxes — useful for cash flow management.
How to Use This Depreciation Calculator (With Example)
This calculator needs four inputs: the asset's purchase cost, its estimated salvage value, its useful life in years, and the depreciation method. It instantly generates a full year-by-year schedule.
Scenario: "SteelCraft Fabrication" — CNC Machine Purchase
- Asset Cost: $80,000 (CNC milling machine including installation)
- Salvage Value: $8,000 (estimated scrap metal value after 10 years)
- Useful Life: 10 years
- Method: Straight-Line (machine provides consistent output throughout its life)
The Results
Annual Depreciation: ($80,000 − $8,000) ÷ 10 = $7,200/year
Each year, SteelCraft records $7,200 as a non-cash depreciation expense on its P&L, reducing taxable income. Over 10 years, the machine goes from $80,000 on the balance sheet to its $8,000 salvage value. If SteelCraft is in the 25% tax bracket, this saves $1,800/year in taxes.
Straight-Line vs. Declining Balance: When to Use Each
The right method depends on how the asset's economic value is actually consumed over time.
Use Straight-Line when the asset delivers roughly equal value each year: office furniture, buildings, shelving, heavy machinery, manufacturing equipment. It's also simpler to manage and explain to stakeholders.
Use Declining Balance when the asset becomes obsolete or loses its highest utility quickly: computers, vehicles, smartphones, software. A laptop is most productive in Year 1 when it's fast and new — by Year 5, it may struggle to run modern software. Front-loading the expense better matches the economic reality.
Understanding Book Value vs. Tax Depreciation
This is one of the most misunderstood aspects of business accounting, and it trips up many small business owners.
Book Depreciation (what this calculator computes) is what you record on your financial statements (P&L and Balance Sheet). It uses GAAP-approved methods like straight-line or declining balance and is designed to match costs to the periods the asset generates revenue.
Tax Depreciation (what you report to the IRS) uses the Modified Accelerated Cost Recovery System (MACRS), which assigns every asset to a specific class life (3, 5, 7, 15, 20, 27.5, or 39 years) and applies a front-loaded depreciation table. Additionally:
- Section 179: Allows businesses to immediately expense the full cost of qualifying equipment (up to $1.16M for 2023) in the year of purchase instead of depreciating over time.
- Bonus Depreciation: Allows an additional first-year deduction (60% for 2024, phasing down) on qualifying new and used property.
The result is that your book income and your taxable income will often differ significantly — especially in the early years of an asset's life. Always consult a CPA for tax planning.
Common IRS Useful Life Estimates (MACRS)
When setting up your depreciation schedule, here are the IRS MACRS class lives most commonly applied to business assets:
- 3-Year Property: Small tools, certain livestock, tractor units
- 5-Year Property: Computers, office equipment, cars, light trucks, research equipment
- 7-Year Property: Office furniture, fixtures, most manufacturing equipment
- 15-Year Property: Land improvements, fences, parking lots, certain restaurants
- 39-Year Property: Commercial real estate buildings
Frequently Asked Questions
What is straight-line depreciation?
Straight-line depreciation is the simplest and most common method. It assumes an asset loses an equal amount of its value every year of its useful life until it reaches its salvage value.
What is declining balance depreciation?
The declining balance method is an accelerated depreciation method. It assumes an asset loses more value in early years — commonly used for assets that become obsolete quickly, like computers and vehicles.
What is salvage value?
Salvage value (or residual value) is the estimated amount you expect to sell the asset for at the very end of its useful life. Enter 0 if the asset will have no value remaining.
Why do businesses record depreciation?
Depreciation is a non-cash expense that reduces taxable income without an actual cash outflow (the cash left when the asset was purchased). It matches the cost of the asset to the years it generates revenue — a core principle of accrual accounting.
What is the difference between book and tax depreciation?
Book depreciation (recorded on your financial statements) uses methods like straight-line to match expenses to revenue. Tax depreciation (IRS) uses MACRS schedules and may allow accelerated write-offs like Section 179 or Bonus Depreciation, which can differ significantly from book depreciation.