ReckonBoxHow fast an asset writes off
A depreciation calculator spreads the cost of an asset across the years it is used, and which method you pick changes how much you deduct each year. For a US business, the method that matters for tax is MACRS, and it is the one calculator the field leaves out.
On a $50,000 asset in the 5-year class, MACRS deducts $10,000 in year one and $16,000 in year two, front-loaded on purpose. Straight line on the same asset is a flat $9,000 a year. That gap, larger deductions sooner, is why the tax method and the book method are not the same thing.
The method every other calculator skips
MACRS is the Modified Accelerated Cost Recovery System, the method US businesses use to depreciate assets for federal tax, and no other ranked calculator includes it. calculator.net and Enerpize do straight line, declining balance, and sum-of-the-years-digits, all book methods, and stop there.
The difference is not academic. A business keeps two sets of depreciation: a book method for its financial statements and MACRS for its tax return. MACRS applies fixed percentages from IRS Publication 946 to the original cost, ignores salvage value, and front-loads the write-off. Leaving it out means the calculators answer the accounting question while the reader is usually asking the tax one.
The half-year convention that adds a year
MACRS treats every asset as placed in service at the midpoint of the year, so a 5-year asset actually depreciates across 6 tax years. That half-year convention is why the IRS tables carry one more row than the class name suggests.
You get half a year of depreciation in year one, which pushes the last half into an extra year at the end. A 7-year asset spans 8 years, a 10-year asset spans 11. The full schedule for the default asset shows the shape:
| Year | Depreciation | Book value |
|---|---|---|
| 1 | $10,000 | $40,000 |
| 2 | $16,000 | $24,000 |
| 3 | $9,600 | $14,400 |
| 4 | $5,760 | $8,640 |
| 5 | $5,760 | $2,880 |
| 6 | $2,880 | $0 |
Where the numbers come from
For MACRS, the tool multiplies each year percentage from the IRS half-year table by the asset original cost. The 5-year figures are 20%, 32%, 19.20%, 11.52%, 11.52%, and 5.76%, which is why year two is the largest. Salvage value is ignored, so the asset depreciates fully to zero.
The book methods use the depreciable base, the cost minus salvage. Straight line divides it evenly by the useful life. Declining balance applies a multiple of the straight-line rate to the falling book value and stops at salvage. Sum-of-the-years-digits weights each year by remaining life, so a 5-year asset takes 5/15 of the base first, then 4/15, and so on.
What this does not decide for you
This shows the depreciation schedules, not your tax return. It does not model the Section 179 expensing election or bonus depreciation, both of which can let a business write off far more in year one, the mid-quarter convention that applies when most assets are bought late in the year, or the recapture tax when you sell a depreciated asset for a gain. Real estate uses its own 27.5-year and 39-year schedules, which the rental property tool covers.
None of this is advice on how to depreciate your own assets. Depreciation rules turn on asset type, timing, and elections that a return has to get right. For your business, a CPA is the right call.
Frequently asked questions
What is MACRS depreciation? MACRS is the Modified Accelerated Cost Recovery System, the method US businesses use to depreciate assets for federal tax. It ignores salvage value, applies fixed IRS percentages from Publication 946 to the original cost, and front-loads the deduction. On a $50,000 asset in the 5-year class, the first-year deduction is $10,000 and the second year $16,000.
Why does MACRS 5-year property take 6 years? Because of the half-year convention, which treats every asset as bought at the midpoint of the year. That gives half a year of depreciation in year one, so the remaining half spills into an extra year. A 5-year asset depreciates across 6 tax years, a 7-year asset across 8, and so on, which is why the IRS tables have one more row than the class name.
What is the difference between MACRS and straight-line depreciation? Straight-line spreads the cost minus salvage value evenly over the useful life, while MACRS front-loads the deduction and ignores salvage. On a $50,000 asset with $5,000 salvage over 5 years, straight-line gives $9,000 every year, while MACRS gives $10,000 then $16,000 in the first two years. Businesses use MACRS for tax and a book method for their financial statements.
How is declining balance depreciation calculated? Declining balance applies a fixed rate to the falling book value each year, so the deduction is largest early and tapers off. Double declining balance uses twice the straight-line rate: on a $50,000 asset over 5 years, that is 40% of book value, or $20,000 in year one. It stops once the book value reaches the salvage value.
What is sum-of-the-years-digits depreciation? Sum-of-the-years-digits is an accelerated book method that weights the deduction by remaining life. For a 5-year asset the digits sum to 15, so year one takes 5/15 of the depreciable base, year two 4/15, and so on. On a $45,000 base that is $15,000 in year one, more than straight-line but less front-loaded than double declining balance.
Does MACRS use salvage value? No. MACRS ignores salvage value entirely and depreciates the full cost to zero, unlike the book methods, which stop at the salvage value. That is one reason the tax deduction under MACRS is larger overall than a straight-line schedule that leaves a salvage amount on the books.