To calculate the book value of an asset, subtract accumulated depreciation from the asset’s acquisition cost. That single subtraction is the whole formula. The work sits in getting each input right: what you actually paid to put the asset in service, and how much depreciation has piled up against it since.
The Formula, With a Worked Example
Book Value = Acquisition Cost − Accumulated Depreciation
Say a company buys a commercial printing press for $100,000 and records $40,000 of depreciation over three years. Book value is $100,000 minus $40,000, which is $60,000. That figure sits on the balance sheet under long-term assets and represents the portion of the original cost not yet expensed. For intangible assets, the mechanics are identical; the word just shifts from depreciation to amortization.
What Goes Into Acquisition Cost
Acquisition cost is more than the sticker price. It includes every expense needed to get the asset ready for use: the purchase price, sales tax, freight, installation, and testing.1Internal Revenue Service. Publication 946 (2025), How To Depreciate Property A $50,000 machine that costs $2,000 to ship and $3,000 to install has an acquisition cost of $55,000. That full $55,000 is the starting point.
Costs incurred after the asset is already in service don’t get folded in. Routine maintenance, for example, is expensed the year it happens and doesn’t touch book value. The higher your acquisition cost, the higher your starting book value, and the more depreciation there is to record over the asset’s life.
Building Up Accumulated Depreciation
Accumulated depreciation is the running total from the day the asset was placed in service through today. How fast that total grows depends on the method you use.
Straight-Line
The most common method. Subtract the expected salvage value from the acquisition cost, then divide by the useful life in years:
Annual Depreciation = (Cost − Salvage Value) ÷ Useful Life
A delivery van bought for $40,000, with a $5,000 salvage value and a five-year life, produces $7,000 of depreciation each year. After three years, accumulated depreciation is $21,000 and book value is $19,000. Every year looks the same.
Double-Declining Balance
An accelerated method that front-loads depreciation into the early years:
Annual Depreciation = Book Value at Start of Year × (2 ÷ Useful Life)
Take the same van. The rate is 2 ÷ 5, or 40%. Year one depreciation is $16,000 (40% of $40,000), dropping book value to $24,000. Year two depreciation is $9,600 (40% of $24,000), taking book value to $14,400. The annual charge shrinks because it’s always a percentage of a declining base. At some point you switch to straight-line for the remaining balance so the asset is fully depreciated. Salvage value doesn’t appear in the annual formula, but depreciation stops once book value reaches the salvage amount.
Units of Production
When wear depends on usage rather than time, this method ties depreciation to output. Divide the depreciable base (cost minus salvage) by total expected units, then multiply by units produced in the period. A machine expected to produce 100,000 units over its life with a $90,000 depreciable base generates $0.90 of depreciation per unit. If it produces 15,000 units in a year, depreciation is $13,500. Common for manufacturing equipment and vehicles where mileage matters more than the calendar.
Tax Book Value Is a Different Number
For federal tax purposes, you don’t pick your own useful life. The IRS assigns recovery periods through the Modified Accelerated Cost Recovery System (MACRS), and salvage value is treated as zero.2Office of the Law Revision Counsel. 26 USC 168 – Accelerated Cost Recovery System The result is that tax book value (called “adjusted basis”) rarely matches the book value on your financial statements.
The most common MACRS recovery periods are:
- 5-year property: vehicles, computers, and certain machinery
- 7-year property: office furniture and fixtures
- 15-year property: qualified improvement property and land improvements
- 27.5 years: residential rental buildings
- 39 years: nonresidential real property (offices, warehouses, retail)
The default method for most personal property under MACRS is 200% declining balance, switching to straight-line when that produces a larger deduction. Real property uses straight-line only.2Office of the Law Revision Counsel. 26 USC 168 – Accelerated Cost Recovery System Timing conventions also affect the first-year figure. The half-year convention is the default and treats every asset as placed in service at midyear. If more than 40% of your total purchases for the year happen in the last quarter, the mid-quarter convention applies instead.
Two provisions can drop tax book value much faster. The Section 179 deduction lets qualifying businesses expense up to $2,560,000 of asset costs in 2026, phasing out dollar-for-dollar once qualifying property placed in service exceeds $4,090,000. Sport utility vehicles have a separate $32,000 cap. Section 179 can’t create or increase a business loss, so you need enough income to absorb it. Bonus depreciation, permanently restored at 100% for qualifying property acquired and placed in service after January 19, 2025, allows you to deduct the entire cost of eligible assets in year one and can create a loss.1Internal Revenue Service. Publication 946 (2025), How To Depreciate Property
The upshot: a $200,000 machine you fully expensed for taxes has a tax book value of zero even while it sits on your shop floor with a financial book value in the six figures.3Internal Revenue Service. Book to Tax Terms When someone asks for an asset’s book value, confirm whether they want the GAAP figure or the tax basis. The two answers can differ by tens of thousands of dollars.
Adjustments After the Purchase
Book value isn’t set in stone once depreciation starts. Two events change it: capitalized improvements push it up, and impairment writes it down.
If you spend money on an existing asset and that spending qualifies as an improvement, the cost is added to book value and depreciated over time rather than expensed immediately. The IRS defines an improvement as a betterment, a restoration, or an adaptation to a new or different use.4Internal Revenue Service. Tangible Property Final Regulations Betterments materially increase capacity, productivity, efficiency, or quality, or fix a defect that existed before you acquired the asset. Restorations replace a major component, return a non-functional asset to working condition, or rebuild something to like-new condition after the end of its class life. Adaptations convert an asset to a use fundamentally different from its original purpose. Routine repairs and maintenance keep the asset in its current condition and are expensed right away.
Small purchases can skip the capitalization analysis under the de minimis safe harbor: businesses with audited financial statements can expense items costing up to $5,000 per invoice, and those without can expense items up to $2,500 per invoice.4Internal Revenue Service. Tangible Property Final Regulations
Impairment cuts the other way. If an asset’s carrying amount overstates what it’s actually worth, GAAP requires a write-down. You first compare the carrying amount to the total undiscounted future cash flows the asset is expected to generate through use and disposal. If the carrying amount is higher, you measure the impairment loss as the difference between carrying amount and fair value.5SEC EDGAR. Note 12 – Long-lived Assets A fleet with a $100,000 book value and a fair value of $70,000 gets a $30,000 impairment charge, and the new book value is $70,000. Under U.S. GAAP that reduction is permanent even if conditions improve later. Goodwill and other intangibles with indefinite lives aren’t amortized at all but are tested for impairment at least annually.6Financial Accounting Standards Board. Summary of Statement No. 142
Book Value of Intangible Assets
Patents, copyrights, customer lists, and similar assets use the same formula, but the annual charge is called amortization. Most finite-lived intangibles have a salvage value of zero because the rights simply expire. A patent bought for $20,000 with a ten-year remaining legal life produces $2,000 of annual amortization. After four years, accumulated amortization is $8,000 and book value is $12,000. Straight-line is standard unless the pattern of economic benefit calls for something else.
Book Value When You Sell
The number you’ve been tracking determines the gain or loss at disposal. The calculation mirrors IRS Form 4797:
Gain or Loss = Sale Price − Adjusted Basis
Adjusted basis is acquisition cost minus all depreciation taken to date, which is exactly the tax book value at the time of sale.7Internal Revenue Service. 2025 Instructions for Form 4797 – Sales of Business Property Sell a machine with an adjusted basis of $15,000 for $22,000 and you have a $7,000 gain. Sell it for $10,000 and you have a $5,000 loss. Gains on personal business property carry a further wrinkle: depreciation recapture. For Section 1245 property (equipment, vehicles, furniture), any gain up to the amount of prior depreciation is taxed as ordinary income rather than at capital gains rates.8Office of the Law Revision Counsel. 26 USC 1245 – Gain From Dispositions of Certain Depreciable Property Accurate book value records are what let you prove your basis when the sale happens.
Book Value Is Not Fair Market Value
Book value looks backward at what you paid and how much you’ve depreciated. Fair market value is what a buyer would pay today. The two drift apart routinely. Commercial real estate bought for $500,000 and depreciated to $350,000 might be worth $800,000 if the neighborhood appreciated. Specialized manufacturing equipment with a $200,000 book value can be worth near zero if the technology is obsolete. Book value governs financial reporting, tax filings, and future depreciation. Fair market value governs sales, insurance, and lending decisions. When the gap grows large enough, it can be the signal that triggers an impairment test.