Real Estate Tax Calc
What a house hack is
House hacking means living in one part of a property while renting the rest — a duplex where you occupy one unit and rent the other, or a single-family home where you rent out spare bedrooms. The rental income offsets your housing cost, and you can depreciate the rented portion of the property under MACRS over 27.5 years.
How to calculate the rental percentage
For a multi-unit building with equally sized units, the rental percentage is simply the number of rented units divided by total units (e.g., 1 of 2 = 50%). For a single-family home with rented rooms, use the ratio of the rented rooms' square footage to the total square footage of the entire home. Apply that percentage to the building's depreciable cost (land excluded) to get the annual depreciation deduction.
Tax implications and limits
All expenses are split: the rental percentage applies to depreciation, mortgage interest (Schedule E portion), property insurance, and repairs. The remaining personal percentage follows homeowner rules — Schedule A for mortgage interest and taxes, no depreciation. When you eventually sell, only the rental portion is subject to depreciation recapture. A formal log of rental vs. personal days and a square-footage calculation provides the audit trail you would need to support the allocation.
A worked example: renting one bedroom
Suppose you buy a $400,000 single-family home; a reasonable land allocation is 20%, leaving a depreciable building basis of $320,000. The home is 2,000 square feet and you rent one 400-square-foot bedroom plus grant the tenant shared use of common areas. A defensible approach counts the private 400 sq ft as fully rental and allocates part of the shared common space; a simpler, conservative method uses just the private room — 400 ÷ 2,000 = 20%. Applying 20% to the $320,000 building basis gives $64,000 of depreciable rental basis. Over 27.5 years under MACRS straight-line, that is roughly $2,327 of annual depreciation. The same 20% is applied to mortgage interest, insurance, utilities, and repairs to reach the Schedule E deductions; the other 80% stays personal.
The duplex case: allocating by unit
A two-to-four-unit building you live in is the cleanest house hack for tax purposes because each unit is a distinct space. If you occupy one unit of a duplex with two equally sized units, 50% of the building basis is rental and depreciable, and 50% is your personal residence. Where units differ in size, allocate by square footage rather than a flat headcount. The rented units are reported on Schedule E; your own unit follows homeowner rules. This clean split also makes the eventual sale easier to compute, because the rental and personal portions were tracked separately from day one.
Shared spaces and reasonable allocation methods
The gray area in single-family house hacks is shared space — kitchen, living room, bathrooms, hallways. The IRS requires a reasonable allocation method but does not mandate a single formula. Two common approaches: (1) count only the tenant's exclusive space (most conservative), or (2) count exclusive space plus a pro-rata share of common areas the tenant is entitled to use. Whichever you choose, apply it consistently to depreciation and to every split expense, and document the square-footage math. Renting to multiple roommates increases the rental percentage; renting the basement or a garage apartment with its own entrance strengthens the case for a larger, well-defined rental portion.
Section 121 exclusion when you sell
House hacking interacts with the Section 121 home-sale exclusion — up to $250,000 of gain ($500,000 married filing jointly) tax-free if you owned and used the home as your main residence for at least two of the last five years. The personal portion of your gain can qualify for the exclusion. Two caveats: the exclusion does not apply to the rental portion's gain that reflects the depreciation you took, and depreciation claimed after May 6, 1997 must be recaptured as unrecaptured Section 1250 gain (taxed up to 25%) regardless of the exclusion. If the rented space is within the same dwelling unit (renting a bedroom, not a separate unit), IRS rules are actually more favorable — you generally do not have to allocate the gain between business and residential use, though you still recapture depreciation.
Common mistakes house hackers make
The frequent errors: forgetting to remove land from basis before depreciating; skipping depreciation to keep reporting simple (a costly mistake, because recapture at sale is based on depreciation allowed or allowable — the IRS taxes you as if you took it even when you did not); using an aggressive rental percentage without square-footage support; and double-counting expenses by deducting 100% of a shared cost on Schedule E. Also watch the personal-use rules: because you live there, the vacation-home limitations of Section 280A can apply to the personal share, and the deductible rental loss may be limited. Keep a simple file — floor plan with square footage, a rental-vs-personal calendar, and receipts — and the allocation will hold up.
Establishing your starting basis for depreciation
Depreciation begins with the right number. Your depreciable basis for the rental portion is the lesser of your adjusted cost basis or the property's fair market value at the time you place the rented space in service, multiplied by the rental percentage, and then reduced by the land allocation. For a home you bought and immediately began house hacking, cost basis is generally the purchase price plus capitalized closing costs (title fees, recording, transfer taxes — not prepaid interest or insurance). Split the total between land and building using a defensible source such as the county assessor's land-to-improvement ratio or an appraisal; only the building depreciates. If you lived in the whole house first and later started renting rooms, you are converting personal use to rental use, and you must use the lesser-of-cost-or-market rule on the conversion date — a subtle but important step that prevents depreciating a paper gain you never realized.
Which expenses split, and which are 100% deductible
Not every rental expense follows the square-footage percentage. Three buckets exist. Shared/whole-property costs — mortgage interest, property tax, insurance, depreciation, roof or HVAC repairs, exterior painting, utilities you pay — are allocated by the rental percentage. Directly rental costs — repainting only the rented bedroom, a lock for the tenant's door, advertising for the room, tenant screening fees, or a repair inside the rented unit — are 100% deductible on Schedule E because they benefit only the rental. Directly personal costs — improvements to your own bedroom, your personal phone — are not deductible at all. Sorting each expense into the correct bucket, rather than blindly applying one percentage to everything, both maximizes legitimate deductions and keeps the shared-cost allocation clean if the return is ever examined.
The passive loss rules still apply to your rental share
Even a modest house hack can generate a tax loss once you layer depreciation onto the rental percentage of interest, taxes, insurance, and repairs. That loss is generally passive under IRC §469. Most house hackers are not real estate professionals, so the loss is deductible against other income only through the $25,000 active-participation allowance — available if you 'actively participate' (a low bar: approving tenants, setting rent terms) and your modified adjusted gross income is under $100,000, phasing out completely at $150,000. Above $150,000 of MAGI, the rental loss is suspended and carried forward until you have passive income or sell the property. Because house hackers are often earlier in their careers with moderate incomes, many can actually use the allowance — but do not assume the paper loss cuts your tax bill this year without checking where your MAGI falls in the phase-out.
What happens when you move out and rent the whole property
A common house-hack arc is to live in the property for a year or two, then move out and rent every unit or room. On that conversion date, the rental percentage jumps — often to 100% — and your depreciation deduction rises accordingly, calculated on the now-fully-rental building basis (again, lesser of cost or fair market value at conversion for any portion newly placed in service). Keep clear records of the conversion date because it changes the numbers mid-year and starts the clock on the formerly personal portion. Watch the Section 121 interaction too: to exclude gain on the portion that was once your residence, you generally need two years of use as a main home within the five years before sale, so selling several years after fully converting can cause the home-sale exclusion to lapse. Investors who want both the exclusion and continued rental income sometimes sell within that window or plan a 1031 exchange for the rental portion.
Frequently asked questions
Can I depreciate my primary home if I rent out rooms?
Only the rented portion. Use the square footage of the rented space divided by total square footage, then apply that percentage to the building's cost basis.
What happens to depreciation when I stop house hacking?
Depreciation stops on the date you convert back to full personal use. Any deferred recapture on the rental portion applies if you later sell.
How do I handle shared spaces like the kitchen and living room?
Use a reasonable, consistent method. You can count only the tenant's exclusive space (conservative) or add a pro-rata share of the common areas they are entitled to use. Whatever you pick, apply the same percentage to depreciation and every split expense, and document the square-footage calculation.
Do I lose the home-sale tax exclusion by house hacking?
Not entirely. The personal portion of your gain can still qualify for the Section 121 exclusion (up to $250,000, or $500,000 married filing jointly). But depreciation you claimed is recaptured regardless, and the gain attributable to a separate rental unit generally does not qualify for the exclusion. Renting a room within the same dwelling unit is treated more favorably than renting a separate unit.
Should I skip depreciation to keep my taxes simple?
No. Recapture at sale is based on depreciation allowed or allowable, so the IRS treats you as having taken it even if you did not — you would owe the recapture tax without ever having received the deductions. Claim the depreciation each year you house hack.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.