Cost Segregation Calculator: How to Estimate Your Savings

The short answer A cost segregation calculator estimates your first-year depreciation deduction by reclassifying a portion of your building's value (typically 20 to 35 percent) into shorter 5, 7 and 15-year lives, then multiplying the resulting deduction by your marginal tax rate to approximate the tax you defer. Land is excluded because it never depreciates. Use it to size the opportunity, then confirm the real numbers with an engineered study and your tax advisor. You can run the math now with our cost segregation calculator.

What a cost segregation calculator actually does

When you buy a rental or commercial property, the IRS normally makes you depreciate the building slowly, over 27.5 years for residential or 39 years for commercial. Cost segregation has an engineer break the building into its components and move the parts that qualify, such as flooring, cabinetry, specialty electrical, fixtures and land improvements, into much shorter recovery periods. That pulls a large chunk of depreciation forward into the early years of ownership.

A calculator models this in simplified form. It takes your inputs, applies a reasonable reclassification percentage based on the property type, and estimates the extra depreciation you could claim in year one. The output is an estimate of a tax deferral, not a permanent tax cut, and not a guarantee. The real figure depends on a property-specific engineering analysis. For the underlying mechanics, see our guides on what cost segregation is and how cost segregation works.

The inputs you need

A good estimate needs only a handful of numbers, and the quality of the estimate depends entirely on getting these right:

• Purchase price. What you paid for the property, including certain closing and acquisition costs that get added to basis.
• Land value. Land does not depreciate, so it must be carved out first. Many investors use the land-to-building split from their county tax assessment as a starting point.
• Property type. Residential rental, short-term rental, retail, office, warehouse and multifamily all tend to reclassify at different rates because they contain different components.
• Your marginal tax rate. The deduction is worth your top federal rate, plus any state rate, on the income it offsets.
• Placed-in-service date. This matters because bonus depreciation rules depend on when the property was put into service.

The formula behind the estimate

Strip away the interface and almost every calculator follows the same four steps:

• Step 1. Subtract land value from the purchase price to get your depreciable building basis.
• Step 2. Multiply the building basis by an assumed reclassification percentage (commonly 20 to 35 percent) to find the value moving into short-life categories.
• Step 3. Apply the applicable depreciation treatment to that reclassified amount to estimate the first-year deduction. When bonus depreciation applies, a large share of the 5, 7 and 15-year property can be deducted immediately.
• Step 4. Multiply the first-year deduction by your combined marginal tax rate to approximate the tax you defer in year one.

One current factor worth understanding: under the One Big Beautiful Bill Act, 100 percent bonus depreciation was restored for qualifying property placed in service after a date in early 2025. That substantially increases how much of the reclassified value can be deducted in the first year, which is why interest in cost segregation has climbed in 2026. Because the effective dates and rules are specific, confirm your situation with a CPA rather than relying on a calculator's assumptions.

A worked example

Here is an illustrative estimate for a residential rental. The figures are examples only, chosen to show the method, not a promise of results. Assume a $1,000,000 purchase price, a 20 percent land allocation, a 25 percent reclassification into short-life property, 100 percent bonus depreciation on that reclassified amount, and a combined 35 percent marginal tax rate.

Step	Figure
Purchase price	$1,000,000
Less land (20%)	-$200,000
Depreciable building basis	$800,000
Reclassified to short-life (25%)	$200,000
Estimated first-year deduction	$200,000
Estimated first-year tax deferral (35%)	$70,000

In this example the owner accelerates roughly $200,000 of depreciation into year one and defers about $70,000 of tax. Change any input and the result moves: a higher land allocation lowers it, a higher reclassification percentage or tax rate raises it. This is exactly why a calculator is a starting point and an engineered study is the finish line.

Typical reclassification by property type

The single input that swings a calculator estimate the most is the reclassification percentage, and it is not one number for every building. Different property types hold different proportions of short-life components, such as decorative finishes, specialty electrical, process plumbing and site improvements. The ranges below are general illustrations drawn from how studies tend to come out, not guarantees for any specific property. Your actual percentage can only be established by an engineering analysis.

Property type	Illustrative reclassification range
Single-family rental	About 15% to 25%
Short-term / vacation rental	About 20% to 30%
Multifamily / apartments	About 20% to 30%
Retail and restaurant	About 25% to 35%
Warehouse / industrial	About 10% to 20%

Notice how a restaurant with heavy build-out can sit near the top of the range while a plain warehouse sits near the bottom. If a calculator applies a flat 30 percent to every property, it is overstating the benefit for some owners and understating it for others. The property-type lens is one reason a professional study so often finds more, or sometimes less, than a generic tool predicts.

Short-term rentals and your tax position

Short-term rentals have become one of the most discussed uses of cost segregation, because under certain conditions the losses they generate can offset other income rather than being trapped as passive. A calculator will happily show you a large first-year deduction, but whether you can actually use that deduction this year depends on your participation, your other income, and the passive activity and material participation rules. Those rules are genuinely complex and fact-specific, which is a hard limit on what any calculator can tell you. The estimate shows the size of the deduction; only your tax advisor can confirm how much of it helps you this year. For the full picture of how the strategy fits residential and rental property, see our cost segregation real estate guide.

Where estimates go wrong

Calculators are only as honest as their assumptions, so treat the output with healthy skepticism:

• Guessing the land value. Underestimating land inflates the benefit. The IRS expects a reasonable, supportable land allocation.
• Using an aggressive reclassification percentage. A calculator that assumes 40 percent on an ordinary rental is selling optimism, not accuracy.
• Ignoring your actual tax position. The deduction is only valuable if you have income it can offset. Passive activity rules can limit how losses are used.
• Forgetting recapture. Accelerated depreciation can come back as recapture when you sell, so a quick hold can erode the benefit.

From estimate to decision

A calculator answers one question: is the potential benefit large enough to justify a professional study? If your estimated first-year deferral is many times the likely study cost, the strategy probably deserves a serious look. If the numbers are thin, a short hold or low building value may make it not worth the fee. For a sense of pricing, see our breakdown of what a cost segregation study costs, and to weigh the overall decision, read whether cost segregation is worth it.

Once the estimate looks promising, the next move is a conversation with a qualified provider and your CPA, who will confirm the real reclassification based on an engineering analysis of your specific property. The calculator got you to the table. The professionals get you an audit-defensible number.

Frequently asked questions

How accurate is a cost segregation calculator?

A calculator gives a rough estimate, not a precise figure. It applies an assumed reclassification percentage to your building basis, so the result can be off by a wide margin. Only an engineering-based study produces an audit-defensible number. Treat the calculator as a first filter.

How do you calculate cost segregation savings?

Start with the purchase price, subtract the land value to get your depreciable building basis, multiply that by an assumed reclassification percentage (often 20 to 35 percent) to find the short-life value, estimate the first-year deduction on it, then multiply by your marginal tax rate to approximate the tax you defer.

Do you subtract land before estimating?

Yes. Land does not depreciate, so it must be removed from the purchase price before you estimate any benefit. Many investors use the land-to-building split from their county tax assessment as a reasonable starting point, which a CPA can refine.

What percentage of a building can be reclassified?

It varies by property type and components, but studies commonly reclassify about 20 to 35 percent of the depreciable basis into shorter 5, 7 and 15-year lives. Properties with more specialty systems tend to sit at the higher end, while plain residential rentals sit lower.

Is a calculator estimate enough to file taxes?

No. A calculator estimate is for planning only. To claim accelerated depreciation you need an engineering-based study with proper documentation that you and your CPA use on the return, because the IRS expects property-specific analysis, not a rule-of-thumb figure.

This is general educational information, not tax advice. Cost segregation and depreciation rules are complex and change; consult a qualified CPA or tax advisor before acting.