How to Estimate Your Cost Segregation Savings in 30 Seconds (Free Calculator)

Free cost segregation calculator walkthrough — three numbers in, OBBBA-current 100% bonus rate, §469 PAL gating + §1245 recapture warnings. No email required.

How to Estimate Your Cost Segregation Savings in 30 Seconds (Free Calculator)

Most cost segregation calculators on the internet either gate the result behind a contact form so a sales rep can call you, or quote bonus depreciation rates that the One Big Beautiful Bill Act (OBBBA) made obsolete in July 2025. Neither is useful when you're deciding, today, whether a $3,000–$8,000 engineering study is worth commissioning.

Our free cost segregation calculator takes three numbers, runs an OBBBA-current screening pass, and gives you a Year-1 federal tax-effect estimate in about 30 seconds. No email, no upsell, no sales call. It is a feasibility estimator — not a study, not tax advice, and not a substitute for CPA review. What it is: a fast way to find out whether the math is in the neighborhood before you write a check to an engineering firm.

This walkthrough shows what the calculator asks, what the output means, and the three guard rails — IRC §469 passive activity gating, IRC §1245 recapture, and the OBBBA bimodal 2025 rule — that most "calculator" pages quietly skip.

What a feasibility estimate actually does (vs. a study)

A cost segregation study is a regulated engineering deliverable. A licensed engineer or qualified CPA inspects the property, allocates basis across building components, documents asset classes under the IRS Cost Segregation Audit Techniques Guide, and produces a report you can rely on under Treasury Circular 230. Texas Occupations Code Chapter 901 reserves the word "study" for that work product. We do not do that work.

A feasibility estimate — what our tool produces — runs the same conceptual math against your inputs using simplified heuristics calibrated to IRS Audit Techniques Guide Chapter 7.2 percentages. It is directionally useful, not return-ready, and cannot be relied on under Circular 230. Think Zillow Zestimate, not appraisal.

The honest delta: a real study will typically land within 10–25% of our screening number on a 1–4 unit residential property — higher when an engineer finds detail items the questionnaire missed, lower when the engineer rejects items we counted. The screening's job is to decide whether the $3k–$8k engineering fee is worth paying.

Run the screening for a 2026 long-term rental →

Three numbers you need before you start

Have these handy from your closing disclosure:

1. 1. Purchase price. The full amount you paid, including any seller credits absorbed into basis.
2. 2. Land value. From the closing tax bill or county appraisal district. If you don't have it, the calculator accepts the appraised improvement value and backs into land. (Depreciation applies to the building only, not the dirt.)
3. 3. Year acquired. The tax year placed in service. Drives the IRC §168(k) bonus rate — bimodal in 2025 after OBBBA §70301.

Three optional inputs that meaningfully change the output: federal tax bracket (drives the dollar effect), real-estate-professional status under §469(c)(7) (drives Year-1 usability vs. Form 8582 suspension), and planned holding period (triggers the §1245 recapture warning on flips inside 5 years).

Walking through the calculator — step by step

The flow is six sections. You can complete it in under 60 seconds if you have the closing documents in front of you.

Step 1. Open /cost-seg/ and pick the property use. Long-term rental, short-term rental, mixed-use, or primary residence. This is not cosmetic: long-term residential rentals depreciate over 27.5 years; commercial over 39. Short-term rentals also use 27.5-year recovery but unlock the IRC §469(c)(2) seven-day average-rental carve-out we will gate against later. The reclassification percentages and the PAL gate both depend on this answer.

Step 2. Enter the purchase month and year. The year drives the bonus rate. The month matters in 2025: property acquired on or before January 19, 2025 is stuck on the 40% TCJA tail; property acquired after that date gets OBBBA's 100%. The month also triggers the §168(d)(3) mid-quarter convention on October–December single-property acquisitions. Leaving the month blank on a Q4 buy quietly costs you accuracy.

Step 3. Enter the purchase price. Type it plain — 850000, no commas needed; the field formats as you type. Total acquisition cost is the upper bound on depreciable basis. Title fees, transfer taxes, and recording costs capitalize into basis under Treas. Reg. §1.263(a)-2 — a settlement-costs field downstream captures them.

Step 4. Click "Look up" on the address bar (optional but recommended). If the property is in Montgomery, Harris, Dallas, or Travis County, the lookup pre-fills appraised value, land value, improvement value, square footage, year built, and lot acres from the county appraisal district. (Same pipeline that powers our property tax protest tool.) A county-sourced land allocation is cleaner than a guess; everything is overridable.

Step 5. Enter land value (or improvement value). The calculator needs a land/building split to compute depreciable basis. Land number from your closing tax bill is best; otherwise enter improvement value from the appraisal district and the engine backs into land. Why insist on a split: depreciation applies only to the building. The IRS scrutinizes aggressive splits, especially below 15–20% of basis on suburban lots.

Step 6. Walk the interior + exterior feature checklists. Each box maps to a percentage bump in a specific MACRS class — 5-year for personal property, 15-year for land improvements. The IRS Audit Techniques Guide Chapter 7.2 baseline for residential rental is ~5–15% reclassifiable to 5-year; features push that within a sane range. (The engine caps total reclassification at 50% — beyond that you genuinely need an engineer.) The "20–30% reclassification" on engineering-firm marketing is selection-biased: it's the average of properties on which a study was actually commissioned.

Step 7. Pick your federal tax bracket and REPS status (Section 6). Bracket converts the deduction into a dollar tax effect. REPS — the §469(c)(7) real-estate-professional designation — controls whether the Year-1 deduction is usable against W-2 / business income or suspended on Form 8582. "Not sure" defaults to 32% bracket and surfaces the §469 gate so you see both the gross deduction and the gated cash impact.

Step 8. Click "Generate Estimate." Results render in under a second. No email gate, no "an advisor will contact you" — just the page, with a download button if you want to save it.

Try the screening on a short-term rental →

How our calculator handles OBBBA's bimodal 2025 rule

This is the single most common error in competitor calculators today. TCJA phased bonus depreciation down: 100% in 2017–2022, then 80/60/40/20/0% across 2023–2027. OBBBA (Public Law 119-21, signed July 4, 2025) struck the phase-down and made 100% bonus depreciation permanent — but only for property acquired after January 19, 2025. Property acquired on or before stays on the 40% TCJA tail.

Result: 2025 is bimodal. A duplex bought January 10, 2025 → 40% bonus on reclassified personal property. The same duplex bought January 25 → 100% bonus. A 2.5× swing on identical facts.

Our engine encodes the inflection date directly per IRS Notice 2026-11. Enter the actual purchase month and the calculator picks the right rate. Most "calculator" pages still hard-code the 2023 phase-down — if you see a 2025 estimate quoting 40%, you're looking at a stale page. For 2026 forward, the rate is flat 100% under current law. (Basics FAQ → · 2026 bonus FAQ →)

What the output tells you — and what it doesn't

The headline grid shows four numbers:

• Estimated Year-1 federal tax effect. Your bracket × the accelerated Year-1 deduction.
• Year-1 deduction (accelerated). Total first-year write-off under cost-seg: bonus on accelerable basis + first-year MACRS on the non-bonus remainder + mid-month building S/L.
• Year-1 deduction (standard). What you'd deduct with no cost-seg — straight-line over 27.5 or 39 years.
• Accelerable basis %. The slice of depreciable basis we reclassified into 5/7/15-year property.

What the output does not tell you: whether the engineering study will agree, whether the deduction survives audit, whether your facts trigger a §263A capitalization rule, or how your state conforms to federal bonus. It does not model state tax, AMT interaction, or QBI §199A interplay. Those are CPA conversations.

When the estimate says "above threshold" vs. "below threshold"

The banner uses three neutral labels:

• Above threshold. Year-1 federal tax effect ≥ $5,000 — the screening floor at which property owners commonly evaluate further with a CPA.
• Near threshold. $2,000–$5,000. The math is close enough that the $3k–$8k engineering fee may or may not pencil. Review with a CPA before committing.
• Below threshold. Under $2,000. A study likely costs more than it saves in Year 1 — though prior-year acquisitions can change the math via §481(a) catch-up.

We use neutral language deliberately. We do not tell you that you "should" commission a study, or that we "recommend" one. That decision belongs to you and your CPA. The calculator surfaces the number; the framing is yours.

Run a §481(a) look-back on a 2024 acquisition →

The §469 PAL gate you'll see if you're not REPS

If you mark "no" or "not sure" on REPS and the property is a long-term rental, a red callout fires above the headline: "Heads up — §469 passive-activity rules apply." This is the most-overlooked landmine in cost-seg pitches. IRC §469 treats long-term rental income as passive by default; passive losses can only offset passive income — not W-2 wages, business income, or portfolio income. With no passive income to absorb it, the deduction suspends on Form 8582 until you generate passive income or sell.

Two paths around the gate:

1. 1. REPS under §469(c)(7). Both prongs: 750+ hours/year in real-property trades, and more than half your personal services across all trades in real-property trades.
2. 2. STR carve-out under §469(c)(2). Average rental period of 7 days or less, plus material participation. Common Airbnb / VRBO setups satisfy this — long-stay corporate rentals do not.

If neither applies, the headline tax-effect figure still computes, but cash impact is shown as "~$0" until you sell. Most competitor calculators bury this in a footnote, if at all. We surface it above the headline because it changes whether the Year-1 exercise is worth doing at all. (REPS / PAL FAQ →)

The §1245 recapture warning (when it fires and why)

Reclassified 5/7/15-year personal property is §1245 property. On disposition, accumulated depreciation on §1245 property is recaptured as ordinary income — not the §1250 25% unrecaptured-cap-gain rate that applies to building-shell depreciation. For a short hold, this can claw back most of the Year-1 cash benefit.

The warning fires when:

• You indicate planned disposition within 5 years (any property type), OR
• The property is a short-term rental and you haven't explicitly committed to a 5+ year hold (STRs flip statistically more often than LTRs).

The warning doesn't say "don't do cost-seg." It says: factor recapture into the math first. A 1031 exchange can sometimes defer recapture, an installment sale can spread it, and an outright sale inside 24 months will eat much of the Year-1 benefit. (Recapture FAQ →)

What to do with the result

The results page shows four follow-on artifacts that competitor calculators typically don't:

• Asset breakdown table. How much basis was allocated to each MACRS class — the same table a study produces, at screening detail.
• 10-year depreciation comparison. Standard vs. accelerated side-by-side, with cumulative timing benefit. Cost-seg accelerates timing; total deductions over the building's life are similar.
• "What gets filed" callout. Year-of-acquisition reclassification: Form 4562 Part III, lines 19a/19c/19e/19h-19i. Look-back §481(a) catch-up: Form 3115 with DCN 7 under Rev. Proc. 2024-23 — a method change, not an amended return.
• Download / share buttons. PDF lands locally. The share link is read-only and revocable from the same page if you want your CPA to look without giving them an account.

The conversation with your CPA is then short: here are the numbers, here's the bonus rate, here's the PAL posture, here's the recapture risk if I sell early — should I commission a real study? That conversation, not our screening output, is what you file the return on.

Try the calculator

Free, no email, no sales call. Saves to your account only if you log in. Output explicitly cannot be relied on under Circular 230 — it's a screening tool, treat it as one.

• General entry: /cost-seg/
• LTR, 2026 acquisition: /cost-seg/?purchase_year=2026&property_use=long-term-rental
• STR, 2026 acquisition: /cost-seg/?purchase_year=2026&property_use=short-term-rental
• §481(a) look-back on a 2024 acquisition: /cost-seg/?purchase_year=2024&lookback=true

Three numbers in. About 30 seconds. Decide whether the engineering fee pencils before you write the check.

Sources

• IRC §168(k) — Special allowance for certain property (bonus depreciation)
• One Big Beautiful Bill Act, Pub. L. 119-21, §70301 (signed July 4, 2025) — permanent restoration of 100% bonus depreciation for property acquired after January 19, 2025
• IRS Notice 2026-11 — guidance on the OBBBA bimodal 2025 acquisition rule
• IRC §469 — Passive activity losses and credits limited; §469(c)(2) STR carve-out; §469(c)(7) real-estate-professional status
• IRC §1245 — Gain from disposition of certain depreciable property (ordinary-income recapture)
• IRS Cost Segregation Audit Techniques Guide, Chapter 7.2 — Industry-Specific Guidance: Residential Rental (5–15% personal-property reclassification range for 1–4 unit residential)
• IRS Publication 946, Tables A-1, A-5, A-6 — MACRS percentage tables (half-year and mid-quarter conventions)
• Treas. Reg. §1.263(a)-2, §1.263(a)-4 — capitalization of acquisition and settlement costs
• Rev. Proc. 2024-23, DCN 7 — automatic accounting-method change for cost-segregation §481(a) catch-up
• Texas Occupations Code Ch. 901 — CPA practice scope (informs our identity language as a feasibility-screening tool, not a CPA firm)

Disclaimer. This article describes general federal tax concepts. TaxProtestTx (Nought Labs LLC) is a feasibility-screening tool, not tax advice or a cost segregation study. Calculator output cannot be relied on under Treasury Circular 230. Consult a qualified CPA, EA, or attorney before filing. Results are not guaranteed.