Straight-Line Depreciation: The Formula, Real Examples, and How to Calculate It
Every physical asset your business owns — from laptops and delivery trucks to office furniture and manufacturing equipment — loses value over time. Accounting for that loss of value is called depreciation, and the straight-line method is the simplest and most widely used way to do it.
Yet many small business owners either ignore depreciation entirely or find the concept intimidating. That is a costly mistake. Depreciation directly affects your tax deductions, financial statements, and how accurately you understand your company's net worth.
This guide breaks down straight-line depreciation into plain language, walks through the formula step by step, and shows you exactly how to apply it to real business scenarios.
What Is Straight-Line Depreciation?
Straight-line depreciation spreads the cost of a fixed asset evenly across its useful life. Each year, you record the same depreciation expense until the asset reaches its estimated salvage value — the amount you expect it to be worth when you're done using it.
Think of it this way: if you buy a piece of equipment for $10,000 and expect it to last five years, straight-line depreciation lets you expense a portion of that cost every year instead of taking the entire $10,000 hit in the year you bought it.
This method works on one key assumption — that the asset provides equal economic benefit in every year of its life. A desk, for example, is roughly as useful in year one as it is in year five. For assets like these, straight-line depreciation is a natural fit.
The Straight-Line Depreciation Formula
The formula has three inputs and one output:
Annual Depreciation Expense = (Purchase Price - Salvage Value) / Useful Life
Here's what each term means:
-
Purchase Price (Cost Basis): The total amount you paid for the asset, including sales tax, shipping, and installation costs. If you spent $4,500 on a machine and $500 to ship and install it, your cost basis is $5,000.
-
Salvage Value (Residual Value): Your best estimate of what the asset will be worth at the end of its useful life. Some assets have no salvage value — a specialized software license, for example, might be worthless once it expires.
-
Useful Life: The number of years you expect the asset to be productive in your business. For tax purposes, the IRS assigns standard recovery periods through the Modified Accelerated Cost Recovery System (MACRS), but for internal bookkeeping you can estimate based on your own experience.
Step-by-Step Calculation Examples
Example 1: Office Computer
A graphic design firm buys a new workstation for $3,000. They expect to use it for four years and sell it for $200 afterward.
- Cost Basis: $3,000
- Salvage Value: $200
- Useful Life: 4 years
Annual Depreciation = ($3,000 - $200) / 4 = $700 per year
Each year for four years, the firm records $700 in depreciation expense. The monthly depreciation would be $700 / 12 = approximately $58.33.
Example 2: Delivery Vehicle
A bakery purchases a delivery van for $35,000. They estimate a seven-year useful life and a $7,000 resale value at the end.
- Cost Basis: $35,000
- Salvage Value: $7,000
- Useful Life: 7 years
Annual Depreciation = ($35,000 - $7,000) / 7 = $4,000 per year
After three years, the van's book value on the balance sheet would be:
$35,000 - ($4,000 x 3) = $23,000
Example 3: Office Furniture
A startup furnishes its new office with desks, chairs, and shelving totaling $12,000. They assume a 10-year useful life and zero salvage value since the furniture will be worn out.
- Cost Basis: $12,000
- Salvage Value: $0
- Useful Life: 10 years
Annual Depreciation = ($12,000 - $0) / 10 = $1,200 per year
When there is no salvage value, the entire cost of the asset gets depreciated over its useful life.
How to Record Depreciation in Your Books
Each time you record depreciation, you make two entries:
- Debit Depreciation Expense (income statement account) — this increases your expenses and reduces net income.
- Credit Accumulated Depreciation (balance sheet contra-asset account) — this reduces the carrying value of the asset over time.
For the office computer example above, the monthly journal entry would be:
| Account | Debit | Credit |
|---|---|---|
| Depreciation Expense | $58.33 | |
| Accumulated Depreciation | $58.33 |
Accumulated depreciation is a running total of all depreciation recorded against an asset. It appears on the balance sheet as a deduction from the asset's original cost. The difference between the original cost and accumulated depreciation is called the book value (or net book value).
Common IRS Recovery Periods
While you can choose any reasonable useful life for internal reporting, the IRS has specific recovery periods for tax depreciation under MACRS. Here are the most common categories for small businesses:
| Property Class | Asset Examples |
|---|---|
| 3-Year | Certain specialized tools, rent-to-own property |
| 5-Year | Computers, office equipment, automobiles, light trucks, R&D equipment |
| 7-Year | Office furniture, fixtures, agricultural machinery, most manufacturing equipment |
| 15-Year | Land improvements (fences, roads, parking lots, landscaping) |
| 27.5-Year | Residential rental property |
| 39-Year | Commercial buildings (nonresidential real property) |
Note that for tax purposes, the IRS generally requires MACRS (an accelerated method) rather than straight-line. However, you can elect to use straight-line depreciation for any MACRS property class, and real property (27.5-year and 39-year) actually uses straight-line by default.
Straight-Line vs. Other Depreciation Methods
Understanding when straight-line depreciation makes sense — and when it does not — can save you money and improve the accuracy of your financial reports.
Double Declining Balance
This accelerated method front-loads depreciation, giving you larger deductions in early years and smaller ones later. It's useful for assets like technology or vehicles that lose value quickly in the first few years.
Best for: Assets that become obsolete or lose productivity rapidly.
Sum-of-the-Years' Digits
Another accelerated method that allocates more depreciation to earlier years, though less aggressively than double declining balance. It uses a fraction based on the remaining useful life divided by the sum of all useful life years.
Best for: A middle ground when you want some acceleration but not as much as double declining balance.
Units of Production
Instead of spreading depreciation over time, this method ties it to actual usage — miles driven, units produced, or hours operated. It works well for manufacturing equipment or vehicles where wear depends on how much the asset is used, not simply how old it is.
Best for: Assets whose value loss correlates directly with output or usage.
When Straight-Line Wins
Straight-line is the right choice when:
- The asset provides consistent value each year (furniture, buildings, standard equipment)
- You want simplicity and predictability in your financial planning
- You're depreciating real property (where it's the required method)
- You prefer stable, even expense recognition for internal reporting
Common Mistakes to Avoid
Forgetting to Include All Costs in the Basis
Your cost basis is not just the purchase price. It includes delivery charges, installation fees, sales tax, and any modifications needed to put the asset into service. Underestimating your cost basis means you're underreporting depreciation.
Ignoring Salvage Value
Some business owners set salvage value to zero for every asset. While that's legitimate for assets that will truly be worthless, many items — vehicles, electronics, heavy equipment — have real resale value. Overestimating depreciation by ignoring salvage value can distort your financial statements.
Using the Wrong Useful Life
If you depreciate a five-year asset over ten years, you'll understate expenses each year and overstate the asset's value on your balance sheet. If you use too short a life, you'll do the opposite. Base your estimates on industry standards, IRS guidelines, and your own experience with similar assets.
Not Tracking Assets Individually
Lumping multiple assets together makes it hard to account for disposals, upgrades, or changes in useful life. Track each significant asset separately in your depreciation schedule.
Depreciation and Your Tax Strategy
Depreciation isn't just an accounting exercise — it directly reduces your taxable income. Here are a few tax considerations to keep in mind:
Section 179 Deduction: For qualifying assets, the IRS lets you deduct the full purchase price in the year you buy the asset, up to an annual limit ($1,250,000 for 2025). This is an alternative to spreading the deduction over multiple years through depreciation.
Bonus Depreciation: This provision has allowed businesses to deduct a large percentage of an asset's cost in the first year. The percentage has been phasing down — check current IRS guidelines for the applicable rate.
Straight-Line Election: Even when MACRS allows accelerated depreciation, you can elect straight-line for any property class. This might make sense if you expect your tax rate to increase in future years and want to preserve deductions for when they're more valuable.
Always consult a tax professional to determine the best depreciation strategy for your specific situation.
Building a Simple Depreciation Schedule
A depreciation schedule is a table that tracks each asset's depreciation year by year. Here's what the schedule looks like for the delivery van example:
| Year | Beginning Book Value | Depreciation Expense | Accumulated Depreciation | Ending Book Value |
|---|---|---|---|---|
| 1 | $35,000 | $4,000 | $4,000 | $31,000 |
| 2 | $31,000 | $4,000 | $8,000 | $27,000 |
| 3 | $27,000 | $4,000 | $12,000 | $23,000 |
| 4 | $23,000 | $4,000 | $16,000 | $19,000 |
| 5 | $19,000 | $4,000 | $20,000 | $15,000 |
| 6 | $15,000 | $4,000 | $24,000 | $11,000 |
| 7 | $11,000 | $4,000 | $28,000 | $7,000 |
Notice that the ending book value in year seven equals the salvage value of $7,000. That's exactly how it should work — you never depreciate an asset below its salvage value.
Maintaining a depreciation schedule for all your fixed assets helps you stay organized for tax season, makes financial reporting more accurate, and gives you a clear picture of your asset portfolio's current value.
Keep Your Asset Records Organized
Tracking depreciation across dozens of assets, each with different purchase dates, useful lives, and salvage values, gets complicated fast. Spreadsheets work for a handful of items, but as your business grows, you need a system that can handle the complexity without errors.
Beancount.io offers plain-text accounting that makes depreciation tracking transparent and version-controlled. Every entry is human-readable, every change is auditable, and your data is never locked inside proprietary software. Get started for free and take control of your financial records with a modern, developer-friendly approach to accounting.
