Square Footage Calculator

To calculate square footage for an irregular shape, break it into smaller regular shapes — rectangles, triangles, or circles — calculate each one separately, then add the totals together. For an L-shaped room, divide it into two rectangles. For a room with an angled corner, split it into a rectangle plus a triangle. This method works for any complex floor plan, no matter how irregular. The accuracy depends on how precisely you define the boundaries between sub-shapes, so use straight reference lines wherever possible.

One acre equals 43,560 square feet. To convert acres to square feet, multiply the number of acres by 43,560. To go the other way, divide your square footage by 43,560 to get acres. For quick reference: a half-acre is 21,780 square feet, a quarter-acre is 10,890 square feet, and a typical residential lot in most US suburbs runs 0.15–0.30 acres (6,500–13,000 square feet).

Yes, closets count in finished square footage as long as they’re part of a heated, finished living space. The American National Standards Institute (ANSI Z765) standard — which most US appraisers and real estate listings follow — includes closets, hallways, stairs, and any enclosed area with a finished floor, walls, and ceiling that meets minimum height requirements (typically 7 feet). Unfinished closets, storage areas under stairs, and crawl spaces are excluded.

Most square footage standards require a minimum ceiling height of 7 feet for an area to count as finished living space, with at least 50% of the room reaching that height. Areas with sloped ceilings (under attics or stairs) only count where the ceiling is 5 feet or higher, and only if the average room height meets the 7-foot threshold. This rule is why finished attic and bonus room square footage often differs between appraisers and real estate listings — the calculation method matters.

No, a garage typically does not count toward the finished square footage of a home, even if it’s attached and insulated. Garages are considered unfinished space because they don’t meet the standard requirements (heated, finished walls and ceiling, suitable for year-round living). Converted garages can count as finished square footage if they meet building code for habitable space — proper insulation, heat, finished floors and ceilings, and required egress. Always disclose garage conversions to appraisers, as some lenders require permits to count converted space.

Finished basements count as square footage only when they meet ANSI standards: heated, finished walls and ceiling, minimum 7-foot ceiling height, and proper egress. Even when finished, many appraisers and MLS listings report basement square footage separately from above-grade finished square footage because below-grade space typically appraises at 50–70% of above-grade value. Unfinished basements never count as finished square footage. To measure, calculate the area the same way as any other floor — but report it as a separate line item in listings or appraisals.

Square footage from real estate listings and tax records is often inaccurate, with discrepancies of 5–20% common. Tax records may not reflect additions, conversions, or remodels. MLS listings depend on the source — appraisal-based listings tend to be most accurate, while owner-reported figures vary widely. For any project where square footage matters (renovations, additions, flooring estimates), measure it yourself or hire an appraiser. Trusting public records can mean ordering 10–20% more or less material than you actually need.