Home Office Square Footage Calculator
Calculate home office square footage for tax deduction purposes. The IRS allows you to deduct expenses based on the percentage of your home used exclusively and regularly for business.
Home Office Calculator
IRS simplified vs. regular method
The simplified home office deduction lets you claim $5 per square foot of qualifying office space, capped at 300 sq ft (so a maximum of $1,500). You don't need to itemize home expenses.
The regular method calculates the percentage of your home used for business and applies that percentage to actual home expenses (mortgage interest, utilities, insurance, depreciation). This usually yields a larger deduction but requires more recordkeeping.
Qualifying space requirements
The IRS requires the space be used "exclusively and regularly" for business. A spare room used only as an office qualifies. A dining table where you also eat dinner does NOT qualify, even if you work there 8 hours a day.
The space doesn't need to be a separate room - a clearly defined corner or partitioned area can qualify, as long as it's not used for non-business purposes.
Pro tips
Photograph your space annually
Take dated photos of your home office once a year showing the dedicated work setup. The IRS may request proof of exclusive use during an audit.
Measure to the inside walls
For the regular method, measure both your office and total home to the same standard - typically interior dimensions. Consistency matters more than which method you choose.
Track total home square footage
You need both numbers: office sq ft and total home sq ft. Total home should include all heated finished space - same as ANSI Z765 measurement.
The simplified method has a cap
The $5/sq ft simplified deduction is capped at 300 sq ft / $1,500. If your office is larger or your actual expenses exceed $1,500, the regular method probably saves more.