Home Office Deduction Calculator

Take a self-employed designer with a 200 square foot office in a 2,000 square foot house and $65,000 of profit. The simplified method gives a $1,000 deduction; the regular method on Form 8829 gives $2,809.20, because it captures a share of the mortgage interest, taxes, insurance, utilities and repairs plus depreciation of the house. At a 22% federal bracket and a 5% state rate, that is about $987 of tax saved instead of $351. The calculator runs both methods on the same inputs and applies the limits in the order Form 8829 requires, so it doubles as a Form 8829 calculator.

Who can claim a home office

The deduction belongs to people who run a business: sole proprietors on Schedule C, farmers on Schedule F and partners through Schedule E. Part of the home has to pass the exclusive use test (used only for the business, so a guest room with a desk fails) and the regular use test (ongoing, not occasional). It must also be your principal place of business, a place where you meet clients or customers, or a separate structure such as a detached studio. An office used for billing, bookkeeping and scheduling counts as the principal place of business when you have no other fixed location for that work. Storing inventory when the home is the only fixed location of a retail or wholesale business, and running a daycare that is licensed, has applied for a license or is exempt from licensing, are exempt from the exclusive use test.

W-2 employees get no federal deduction. Unreimbursed employee expenses were suspended for 2018 through 2025, and section 70110 of P.L. 119-21 made the suspension permanent from 2026. Only Armed Forces reservists, qualified performing artists, fee-basis state or local officials and employees with impairment-related work expenses still use Form 2106.

The two formulas

Both results stop at the gross income limit, the business profit before this deduction. Basis is the smaller of cost plus improvements or fair market value when business use began, and land is never depreciated. The 2.564% rate is the straight-line rate for 39-year nonresidential real property that Form 8829 uses for each full year after the first.

Worked example 1: homeowner with a 200 square foot office

The designer's business percentage is 10%. A year of costs comes to $20,400: $9,600 of mortgage interest, $4,200 of real estate taxes, $1,800 of insurance, $3,600 of utilities and $1,200 of repairs. The home's basis is $380,000, including $80,000 of land, and the designer takes the standard deduction.

Neither amount comes near the $65,000 limit. The regular deduction saves $396.93 of self-employment tax, $459.49 of federal income tax and $130.54 of state tax, $986.95 in total, against $351.33 for the simplified method. The extra $1,809.20 of deduction is worth $635.62 a year in exchange for records and depreciation recapture later.

Worked example 2: renter in a small apartment

A freelance translator rents a 900 square foot apartment for $1,800 a month and works in a 150 square foot room, a business percentage of 16.67%. Rent of $21,600, utilities of $1,800 and renter's insurance of $240 total $23,640, and 16.67% of that is $3,940. The simplified method gives only $750. With $48,000 of profit, a 12% bracket and a 5% state rate, the regular method saves about $1,091.30 in tax against $207.74, and a renter never faces depreciation recapture. The smaller the home, the more each square foot of office is worth.

The gross income limit and the order of deductions

Home office costs can reduce business profit to zero but not below. Form 8829 applies them in order: first the business share of mortgage interest and real estate taxes if you itemize, then operating costs (insurance, utilities, repairs, rent and direct costs, plus interest and taxes if you take the standard deduction), and depreciation last. What does not fit carries forward to the next regular-method year.

Suppose the designer instead had a new side business with $1,800 of profit. Operating costs of $2,040 are cut to $1,800, depreciation gets no room, and $1,009.20 carries forward. The simplified method would give $1,000 this year, but anything it could not use would be lost.

Depreciation in the first year of business use

In the first year the depreciation rate depends on the month business use began, because property counts as placed in service mid-month. These are the Form 8829 percentages, applied to example 1's $30,000 business basis.

First-year costs count only for the months of use, and the simplified method counts a month only if the space was used on at least 15 days. Starting in May, the designer gets 8 months: $1,360 of costs plus $481.50 of depreciation, $1,841.50 in all, or $666.67 simplified. Publication 587's own example, a $115,000 basis at 8% first used in May, gives $147.66, and the calculator matches it.

What each $1,000 of deduction is worth

The deduction also lowers self-employment tax. Federal value of $1,000 of deduction for a sole proprietor with $65,000 of profit in 2026, before state tax:

The self-employment part is 15.3% of 92.35% of the deduction below the wage base ($184,500 for 2026, $176,100 for 2025). Some of it comes back as income tax, because a smaller self-employment tax means a smaller deduction for half of it, and the QBI deduction falls by 20 cents per dollar of lower QBI.

When the regular method beats the simplified method

For an office of up to 300 square feet, the office size cancels out: the regular method wins whenever the whole home's yearly costs plus whole-home depreciation exceed $5 times the home's square footage. Example 1's house has $20,400 of costs and $7,692 of building depreciation, $28,092 against a $10,000 bar.

A larger office lowers the bar, because the simplified method stops at $1,500. The shortcut ignores the income limit and the itemizer rule below.

Itemizers: interest and taxes do not double up

If you itemize, the regular method moves the business share of mortgage interest and real estate taxes from Schedule A to Schedule C. That saves self-employment tax but no extra income tax, because you would have deducted those amounts anyway. Tick the itemize box and the calculator accounts for it: in example 1, $1,380 moves and the estimated saving drops from $986.95 to $614.35, still ahead of $351.33. With the simplified method, an itemizer keeps all interest and taxes on Schedule A.

How to use this calculator

1. Choose self-employed or employee and the tax year, which sets the wage base.
2. Enter the office and home square footage and when business use began.
3. Enter a full year of home costs as owner or renter, plus office-only costs and, for owners, basis and land value.
4. Enter profit and tax rates. The headline shows the better method; the tables show the tax saved, carryover and Form 8829 steps.

Key terms

• Direct cost: benefits only the office and is deducted in full.
• Indirect cost: covers the whole home and is deducted at the business percentage.
• Carryover: regular-method costs that did not fit under the limit, usable in a later regular-method year.
• Recapture: the part of a later home sale gain equal to depreciation after May 6, 1997, which the home sale exclusion does not cover.

Limitations

The estimate assumes all business income comes from the home office, one business, one home and no earlier carryovers. It uses marginal rates rather than a full return. Daycare providers use a time-based percentage, and itemizers above the mortgage interest or SALT limits split those costs across different Form 8829 lines.

Related calculators

• For the full self-employment tax on your profit, use the Self-Employment Tax Calculator; for federal income tax, the Income Tax Calculator.
• To expense equipment or a vehicle, use the Section 179 Calculator, and for other assets the Depreciation Calculator.
• To test whether payroll through an S corporation cuts self-employment tax, use the S Corp Tax Calculator.

Sources

• IRS, Publication 587 (2025), Business Use of Your Home: qualifying tests, deduction order, Table 2 percentages, simplified method rules.
• IRS, Instructions for Form 8829 (2025): lines 8 to 44, interest and taxes for standard deduction filers, 2.564% rate.
• IRS, Simplified option for home office deduction, and Revenue Procedure 2013-13.
• U.S. Government Publishing Office, Public Law 119-21, section 70110, and IRS, Instructions for Form 2106 (2025).
• IRS, Topic no. 554, Self-employment tax, and SSA, Contribution and benefit base ($176,100 for 2025, $184,500 for 2026).