The home office deduction comes in two methods: a simplified $5 per square foot, counting at most 300 square feet, or the regular method — your office's share of your actual home expenses. For a 180-square-foot office in a 1,200-square-foot home with $15,000 of expenses, the simplified method gives $900 and the regular estimate gives $2,250. The Home Office Deduction Calculator runs both on your figures; this guide explains the gate both methods stand behind, and what each method asks you to prove.
The gate both methods share
Neither method is available unless the space passes the same test. It must be used regularly and exclusively for business — a desk in a room that doubles as a guest room fails the exclusive-use test no matter how much work happens at it — and it must be the principal place of business, or a place used for meeting clients in the normal course of business, or a separate structure used for the business. The deduction is a self-employment deduction: it is figured for a business reported on Schedule C. W-2 employees are outside it on a federal return under current law, even when the employer requires the homeworking — the gate is about the kind of income, not the reality of the desk.
The two methods, side by side
- Simplified (Revenue Procedure 2013-13): $5 times the square footage used for business, counting at most 300 square feet, so the deduction caps at $1,500. No expense records, no depreciation, no allocation arithmetic — the area is the whole input.
- Regular (Form 8829): the business-use percentage — office area divided by total home area — applied to the home's actual expenses: mortgage interest and property taxes or rent, utilities, insurance, repairs. Direct expenses of the office itself count in full; depreciation of the home enters for owners. Unused amounts limited by business income can carry forward, which the simplified method does not allow.
The choice is annual and reversible: either method can be picked in any year, which is why the comparison is worth running with real figures rather than treating one method as the default. The regular figure the calculator shows is an estimate — Form 8829 applies its own adjustments, including the income limit and depreciation — and it is labelled that way everywhere on this site.
Worked example — a 180 sq ft office in a 1,200 sq ft home
Renata is a self-employed bookkeeper whose spare room — 180 square feet of her 1,200-square-foot home — is used regularly and exclusively for the business, and is her principal place of business. Her home expenses for the year: mortgage interest and property taxes $9,600, utilities $3,000, homeowner's insurance $1,500, and repairs $900 — $15,000 in total:
- Simplified method: 180 sq ft × $5 = $900.00 (the area is under the 300 sq ft cap)
- Business-use percentage: 180 ÷ 1,200 × 100 = 15.00%
- Regular-method estimate: 15.00% × $15,000 = $2,250.00
The regular estimate is $1,350 more than the simplified deduction on these figures — the usual outcome when housing costs are substantial relative to the office area, and the reason the expense records are worth keeping even in years the simplified method wins. Flip the inputs and the verdict flips with them: the same office in a home with $5,000 of total expenses would estimate at $750 by the regular method, and the simplified $900 would be the larger figure. Neither method is the generous one in general; each is generous under different facts.
Try it with your own numbers
This mini-calculator is prefilled with the worked example above and runs the same two formulas as the full tool, with the year's home expenses entered as one total instead of five lines.
Result
—
| Square feet counted (simplified) | — |
| Business-use percentage | — |
| Regular-method estimate | — |
Open the full calculator — the Home Office Deduction Calculator runs the complete version of this calculation.
What to keep, whichever method you file
The simplified method's record-keeping bargain is narrow: it waives the expense receipts, not the proof of the space itself. The measurement of the office and the home, and evidence the room is genuinely a dedicated workspace, are the substantiation either method stands on. Under the regular method the expense trail matters as well — statements for the interest, tax, utility, insurance, and repair figures the percentage is applied to. Like mileage, this is a deduction whose value is set during the year, in records, rather than at filing time; it also lowers the same Schedule C profit that the Self-Employment Tax Estimator taxes and the Mileage Deduction Calculator reduces from the other side, which is why the freelancer deduction set is best treated as one system rather than three separate finds.
For educational and planning purposes only — not professional tax advice. This guide explains the home office methods with a simplified example (one office space, expenses entered as annual totals; the regular figure is an estimate before Form 8829 adjustments, depreciation detail, and the business-income limit). It is not professional tax advice. Verify your eligibility and figures against IRS Publication 587 and review your return with a qualified tax professional.