How To Calculate Depreciation And Amortization | Clear Steps

Depreciation spreads the cost of a physical asset, while amortization spreads the cost of a finite-life intangible asset over time.

If you need to know how to calculate depreciation and amortization, start by splitting the job in two. Depreciation is for physical assets like machinery, vehicles, furniture, and buildings. Amortization is for intangible assets with a limited life, like patents, customer lists, and certain software rights. Once you sort the asset into the right bucket, the math gets much easier.

The point is simple: you do not dump the full cost into one period if the asset will help generate revenue for years. You spread that cost across the periods that receive the benefit. That keeps profit from swinging wildly and gives a cleaner read on what the business earned in each month or year.

What Depreciation And Amortization Mean In Practice

Think of depreciation and amortization as cost-allocation tools. They do not try to guess the resale price every week. They take a long-lived asset, assign a useful life, and push expense into the periods that use it.

Depreciation

Depreciation applies to tangible assets. A machine wears down. A delivery van racks up miles. Office furniture gets used year after year. For those assets, the common straight-line formula is:

(Cost − salvage value) ÷ useful life

Amortization

Amortization applies to many intangible assets with a finite life. A patent may expire after a set number of years. A purchased customer list may have value for a fixed period. In many cases, straight-line amortization is:

Cost ÷ useful life

Some intangibles do not get amortized. Goodwill and some indefinite-life intangibles are handled with impairment testing instead of a fixed annual charge. That distinction matters, because using amortization on the wrong asset can throw off the whole schedule.

How To Calculate Depreciation And Amortization In Four Steps

You can build a clean schedule with four inputs and one method choice. Get those right, and the rest is arithmetic.

1. Set the starting cost. Use the purchase price plus costs tied to getting the asset ready for use. That may include freight, setup, legal fees, filing fees, or installation. If a cost gets the asset into service, it often belongs in the asset balance rather than an immediate expense.

2. Set the useful life. This is the period over which the asset will provide value. Book life can come from company policy, vendor data, wear patterns, legal terms, or accounting standards. Tax life may be different from book life, so do not mix the two schedules.

3. Set the residual or salvage value if one applies. Many tangible assets may have some value at the end of use. Many finite-life intangibles are amortized with no residual value at all. A bad salvage estimate can push annual expense too high or too low.

4. Pick the method. Straight-line is the easiest and most common for book reporting. Some assets fit accelerated methods or units-of-production better. The method should match how the asset loses value or delivers output.

Input	What Goes In	Where It Usually Comes From
Purchase price	Invoice amount paid to acquire the asset	Vendor bill or purchase agreement
Freight and delivery	Costs to bring the asset to your site	Shipping invoices
Installation or setup	Amounts paid to make the asset ready for use	Installer bill or internal project record
Legal or filing fees	Costs tied to securing rights for an intangible asset	Law firm bill or filing receipt
Useful life	Years, months, or output units expected from the asset	Policy manual, contract term, or operating history
Salvage value	Expected value left at the end of use	Resale estimate or scrap estimate
Placed-in-service date	Date the asset starts being used	Receiving record or go-live date
Method	Straight-line, declining balance, or units based	Accounting policy

Formula Examples That Show The Math

Here is the same logic with real numbers. These are book-calculation examples, not a one-size-fits-all tax schedule.

Straight-Line Depreciation Example

Say a business buys a machine for $50,000. Freight and installation add $5,000, so total cost is $55,000. The machine is expected to last five years and be worth $5,000 at the end.

Annual depreciation = ($55,000 − $5,000) ÷ 5 = $10,000

If the company posts depreciation monthly, the monthly expense is $833.33. After one full year, accumulated depreciation is $10,000 and the carrying amount is $45,000.

Straight-Line Amortization Example

Say a company buys a patent for $120,000 and expects to benefit from it for 10 years. If there is no residual value, the math is direct:

Annual amortization = $120,000 ÷ 10 = $12,000

Monthly amortization would be $1,000. After three years, accumulated amortization is $36,000 and the carrying amount is $84,000.

Book rules and tax rules can split here. In the United States, many tax depreciation calculations follow MACRS under IRS Publication 946. Many acquired intangibles fall under section 197 intangibles, which are generally amortized over 15 years for U.S. tax. Under IAS 38 on intangible assets, finite-life intangibles are amortized over their useful life, while indefinite-life intangibles are not.

Which Method Changes The Answer

The method can change both the timing and size of the expense. That matters when you are comparing profit by month, forecasting cash taxes, or valuing a business. Straight-line gives a flat charge. Accelerated methods push more expense into early years. Units-of-production ties expense to output.

Method	How The Charge Is Built	When It Fits Best
Straight-line	Same expense each full period	Assets that provide a steady benefit over time
Double-declining balance	Higher charge early, lower charge later	Assets that lose value faster in early years
Units of production	Expense based on actual output or usage	Machines tied closely to units made or hours used
Tax table method	Expense follows published tax recovery rules	Tax returns where law sets the recovery pattern

When Straight-Line Works Well

Straight-line is common because it is easy to audit, easy to explain, and easy to forecast. If the asset gives a fairly even benefit over its life, straight-line usually feels right. Many businesses use it for office furniture, leasehold improvements, and finite-life intangibles.

When An Accelerated Method Fits Better

Some equipment loses more value in the early years. A declining-balance method can reflect that pattern better than a flat yearly charge. The math is still manageable, though you need to watch the book value so it does not fall below salvage value.

When Units Of Production Fits Better

If a machine’s wear is tied to how much it produces, units-of-production can be a better match. You first set total expected units over the asset’s life, then divide the depreciable base by that number. Each period’s expense depends on actual usage, not just time passing.

Common Mistakes That Skew The Number

• Expensing setup costs that should be part of the asset.
• Using tax life for book reporting with no policy basis.
• Ignoring salvage value on assets that clearly have resale value.
• Amortizing an indefinite-life intangible.
• Forgetting to start the schedule when the asset is placed in service.
• Leaving the schedule untouched after a life change or impairment.

One more trap is partial-year timing. If an asset starts service in the middle of the month or year, many companies prorate the first period for book purposes. Tax rules may use different conventions. If you skip that timing rule, your first-year expense can be off right away.

How The Expense Hits The Books Each Period

Once the annual or monthly number is ready, posting it is plain. Depreciation usually credits accumulated depreciation, which is a contra-asset account. Amortization usually credits accumulated amortization, though some systems credit the intangible asset directly.

• Depreciation entry: Debit depreciation expense, credit accumulated depreciation.
• Amortization entry: Debit amortization expense, credit accumulated amortization.

That entry matters because the original asset cost stays visible on the balance sheet. The accumulated account shows how much of that cost has already been charged to expense. Readers can then see both the original investment and the remaining carrying amount.

Final Check Before Posting The Schedule

Run through this short list before you lock anything in:

• Did you classify the asset correctly as tangible or intangible?
• Did you capture all costs needed to get it ready for use?
• Is the useful life backed by policy, contract terms, or operating history?
• Does the method match the asset’s wear pattern or benefit pattern?
• Are book and tax schedules separated when the rules differ?

Get those points right and the calculation stops feeling slippery. You are just spreading cost with a clear formula, a sensible life, and a method that fits the asset. That is the core of how to calculate depreciation and amortization without getting lost in the jargon.