What MACRS is and why it is not book depreciation
MACRS — the Modified Accelerated Cost Recovery System — is the depreciation method the Internal Revenue Code imposes on most tangible property placed in service after 1986. It is a cost recovery system, not an attempt to measure economic wear. Congress designed it to move deductions forward and stimulate investment, and it shows: MACRS ignores salvage value entirely, assigns recovery periods shorter than real economic lives, and uses accelerated rates for everything except real estate.
Three consequences follow, and they trip up everyone who first meets MACRS after learning book depreciation. You always recover 100% of basis. There is no residual value in the arithmetic, so even a truck you expect to sell for $8,000 is depreciated to zero for tax. The recovery period is statutory, not a judgement. Publication 946 assigns each asset class a life — 5 years for computers, vehicles and office machinery; 7 years for office furniture and most manufacturing equipment; 15 years for land improvements — and you do not get to choose. The first year is never a full year. A convention decides how much of the first year you get, and it decides it by rule, not by your actual in-service date.
Because of all this, your tax depreciation and your book depreciation almost never agree. The gap is a temporary difference: it reverses over the asset's life, and in the meantime it produces a deferred tax liability on the balance sheet. Larger MACRS deductions early mean lower taxable income early and higher taxable income later, with the same total either way.
This calculator covers the General Depreciation System (GDS) for personal property in the 3-, 5-, 7-, 10-, 15- and 20-year classes. It does not cover residential rental property (27.5 years) or non-residential real property (39 years), both of which use straight-line with a mid-month convention, nor the Alternative Depreciation System required for certain listed and tax-exempt-use property.
Where the MACRS percentages come from
Each year's deduction is simply basis multiplied by a published percentage: Dt = B × pt. The interesting question is where pt comes from, and the answer is a mechanical three-part recipe you can reproduce yourself.
Start with a declining balance rate. For 3-, 5-, 7- and 10-year property the rate is 200% of straight-line, so 2 ÷ n. For 15- and 20-year property it is 150%, so 1.5 ÷ n. A 5-year asset therefore depreciates at 40% a year, and a 15-year asset at 10%.
Switch to straight-line when it pays more. Each year, compare the declining balance amount against the remaining basis spread evenly over the remaining recovery period. Declining balance wins early; straight-line wins late; the schedule takes whichever is larger. That switch is what lets the schedule reach zero exactly at the end of the recovery period instead of trailing off asymptotically.
Apply the convention to the first year. Under the half-year convention, every asset is treated as placed in service at the midpoint of the year, so the first year takes half a rate-year and the leftover half spills into an extra tax year at the end — a 5-year asset produces deductions across six tax years. Under the mid-quarter convention, the asset is treated as placed in service at the midpoint of its quarter, so the first-year fraction is (4.5 − q) ÷ 4: 87.5% for the first quarter, 62.5% for the second, 37.5% for the third and 12.5% for the fourth.
Run that recipe for 5-year property under the half-year convention and you get 20.00%, 32.00%, 19.20%, 11.52%, 11.52%, 5.76% — exactly the row printed in Table A-1 of Publication 946. Check the year-4 figure to see the switch happen: declining balance would give 28.80 × 0.40 = 11.52% and straight-line on the remaining 28.80% over the remaining 2.5 years also gives 11.52%, so the schedule flips to straight-line and holds 11.52% for the rest of the period.
This calculator uses the published Table A-1 percentages when you select the half-year convention, so the figures match what you would enter on Form 4562. For the mid-quarter convention it runs the recipe above, which reproduces Tables A-2 through A-5 to the same two decimal places the IRS publishes.
Worked example: $100,000 of 5-year equipment, half-year convention
You place $100,000 of production equipment in service evenly through the year. It is 5-year GDS property, the half-year convention applies because nothing unusual happened in the fourth quarter, and you claim no Section 179 or bonus depreciation.
- Basis subject to MACRS = 100,000 − 0 − 0 = $100,000.
- Year 1: 100,000 × 20.00% = $20,000. Unrecovered basis $80,000.
- Year 2: 100,000 × 32.00% = $32,000. Note that the percentage always applies to the original basis, not the remaining balance — the declining balance mathematics is already baked into the table. Unrecovered basis $48,000.
- Year 3: 100,000 × 19.20% = $19,200. Unrecovered basis $28,800.
- Year 4: 100,000 × 11.52% = $11,520. Unrecovered basis $17,280.
- Year 5: another $11,520. Unrecovered basis $5,760.
- Year 6: 100,000 × 5.76% = $5,760, and basis is fully recovered.
The percentages sum to 100.00%, and the deductions sum to $100,000. At a 21% marginal rate, the first two years alone shelter (20,000 + 32,000) × 0.21 = $10,920 of tax — over half the total shield of $21,000, delivered in the first two of six years. That front-loading is the entire point of the system, and it is why the depreciation tax shield is modelled explicitly in any net present value analysis of an equipment purchase.
Now add elections. Suppose you expense $25,000 under Section 179 and then claim 60% bonus depreciation. Section 179 comes off first: 100,000 − 25,000 = $75,000 remains. Bonus applies to that remainder: 75,000 × 60% = $45,000. Basis subject to MACRS is 100,000 − 25,000 − 45,000 = $30,000, and year 1 MACRS is 30,000 × 20.00% = $6,000. Your total first-year deduction is 25,000 + 45,000 + 6,000 = $76,000, leaving $24,000 of basis to recover across the remaining five tax years.
GDS depreciation rates, half-year convention (Publication 946, Table A-1)
| Year | 3-year | 5-year | 7-year | 10-year |
|---|---|---|---|---|
| 1 | 33.33% | 20.00% | 14.29% | 10.00% |
| 2 | 44.45% | 32.00% | 24.49% | 18.00% |
| 3 | 14.81% | 19.20% | 17.49% | 14.40% |
| 4 | 7.41% | 11.52% | 12.49% | 11.52% |
| 5 | — | 11.52% | 8.93% | 9.22% |
| 6 | — | 5.76% | 8.92% | 7.37% |
| 7 | — | — | 8.93% | 6.55% |
| 8 | — | — | 4.46% | 6.55% |
| 9 | — | — | — | 6.56% |
| 10 | — | — | — | 6.55% |
| 11 | — | — | — | 3.28% |
The 15-year class begins 5.00%, 9.50%, 8.55% and runs 16 tax years; the 20-year class begins 3.750%, 7.219%, 6.677% and runs 21. Select those classes in the calculator to see the full column.
The 40% test decides your convention, and it is tested across the whole year
You do not choose between half-year and mid-quarter. If the total depreciable basis of all MACRS property you place in service during the fourth quarter exceeds 40% of the total basis you place in service all year, the mid-quarter convention is mandatory — and it applies to every asset placed in service that year, not just the fourth-quarter ones. Real property and property placed in service and disposed of in the same year are excluded from the test. A single large December purchase can therefore reduce the first-year deduction on assets you bought in January, which is why the test is worth running before you sign a year-end purchase order.
What this calculator does not do
- It does not apply the Section 179 limits. The dollar cap, the phase-out that reduces it once your total qualifying purchases pass a threshold, and the limitation to your aggregate taxable business income are all indexed or fact-specific. Enter the amount you have already determined you can claim, and check the current Publication 946 for the figures.
- It does not know the current bonus rate. The bonus depreciation percentage has been changed repeatedly by legislation — it was 100% for property placed in service from late 2017 through 2022, then stepped down under the Tax Cuts and Jobs Act schedule, and later statutes revised it again. Enter the rate that applies to your acquisition date.
- It does not cover real property. Residential rental property (27.5 years) and non-residential real property (39 years) are depreciated straight-line under a mid-month convention, which is a different table entirely.
- It does not handle disposals. In the year you sell or scrap the asset you generally take a partial deduction under the applicable convention — half a year under the half-year convention — and then compute gain or loss against the adjusted basis. Section 1245 recapture then taxes gain as ordinary income to the extent of depreciation taken.
- It does not apply the listed-property rules. Passenger automobiles are subject to annual depreciation caps, and property used 50% or less for business must use the Alternative Depreciation System with straight-line recovery.
- It is not tax advice. Class lives, elections and limits turn on facts about your business. Confirm the treatment with a qualified tax preparer before filing Form 4562.
How to read the result and what to do with it
Read the first-year deduction as a cash-flow event, not an expense. Multiply it by your marginal tax rate — federal plus state — and that product is the cash you keep this year instead of paying. On $100,000 of 5-year property with no elections, a 21% federal rate turns the $20,000 first-year deduction into $4,200 of deferred tax. With a Section 179 election covering the whole asset, it becomes $21,000 in year one. The total is identical across the asset's life; what changes is when you get it, which is exactly the variable a discount rate prices.
Compare the MACRS schedule to your book schedule to size the deferred tax liability. If book depreciation on the same $100,000 asset is straight-line over eight years with $10,000 salvage, book charges $11,250 a year while MACRS charges $20,000 in year one. The $8,750 difference multiplied by your tax rate is the deferred tax expense you record, and it reverses in later years when MACRS runs out and book depreciation continues.
Use the unrecovered basis figure when you plan a disposal. Gain on sale is proceeds minus adjusted basis, and because MACRS drives basis toward zero much faster than the asset loses value, equipment sold in year three or four routinely produces a taxable gain even when it sold for less than you paid. Under Section 1245 that gain is recaptured as ordinary income to the extent of the depreciation you claimed — not capital gain — which can make an apparently sensible mid-life upgrade more expensive than it looks. Fold that recapture into the incremental cash flows before running an internal rate of return or a payback period on the replacement.
Finally, keep the accelerated deduction in perspective when reading financial statements. MACRS affects the tax return, not the income statement, so it changes cash taxes and deferred tax but leaves reported operating profit and EBITDA untouched. A company with heavy recent capital spending can show a low effective cash tax rate for several years purely from timing, with no change in profitability at all.
MACRS, ADS and the book methods it sits beside
MACRS is one of three schedules you may end up maintaining for the same asset, and they answer different questions. The GDS schedule in this calculator is what goes on Form 4562 and drives your federal taxable income. The ADS schedule — the Alternative Depreciation System — uses longer class lives and straight-line recovery and is mandatory for property used 50% or less for business, for tax-exempt use property, and for taxpayers who elect out of bonus depreciation in certain circumstances. The book schedule follows ASC 360 or IAS 16 and reflects your own estimate of useful life and residual value.
The underlying mathematics of GDS is not exotic: it is the declining balance method with a straight-line switch, the same machinery the double declining balance calculator exposes directly. What MACRS adds is the statutory recovery period, the zero salvage assumption and the convention. If you want to see the mechanics without the tax rules layered on top, build the schedule there first, then come back and compare year by year.
Many small businesses keep only one set of numbers and use MACRS for their financial statements as well. That is not GAAP, and it matters once you need audited statements, a bank covenant calculation or a valuation, because accelerated tax depreciation understates early book profit and understates the carrying amount of the asset base. If you are heading toward outside financing, keep the book schedule separate from the start — reconstructing several years of it later is far more work than maintaining it, and the difference between the two is exactly what your deferred tax balance is supposed to represent.
Finally, note where MACRS does not reach. Intangibles acquired in a business acquisition are amortised over 15 years under a separate rule; inventory is never depreciated; and repairs versus improvements is decided by the tangible property regulations, not by MACRS. Getting an expenditure into the right bucket changes the deduction far more than choosing between conventions does.