How do you calculate the square footage of a house?

Measure the length and width of each room in feet and multiply them together. Sum the results for all rooms to get total square footage. For example, a 12-foot × 15-foot room is 180 square feet. Include closets and hallways (they count as livable space). Exclude garage space, unfinished basements, and exterior walls. For irregular rooms, break them into rectangles and add the sections.

What counts as livable square footage?

Livable (or gross living area / GLA) square footage includes all heated and cooled interior spaces that are finished and above grade (at or above ground level). This includes bedrooms, bathrooms, living areas, kitchens, hallways, closets, and finished attic space with adequate ceiling height (typically 7 feet or more). It excludes: garages, unfinished basements, porches, decks, and any below-grade space.

Does a finished basement count as square footage?

It depends on the standard used. Under ANSI/RESNET standards (used by most appraisers), finished basements below grade do NOT count toward gross living area (GLA). However, they may be listed separately as 'finished lower level' square footage, which adds value but is counted differently. Some MLS listings include below-grade space — always clarify with the listing agent what is included in the advertised figure.

How accurate are county tax record square footages?

County tax records are frequently inaccurate — sometimes by 100–500 square feet or more — because they may rely on old measurements or permit records. Never rely solely on tax records when buying or selling. Always verify with an appraisal or your own measurement. If the tax record is wrong in your favor (records show less than you have), correcting it could increase your property tax.

How do I measure square footage of an L-shaped or irregular room?

Break the irregular shape into rectangles. For an L-shaped room: divide it into two rectangles, measure each (length × width), and add the results. For example, an L-shape that is 10×20 in one section and 8×10 in the other = 200 + 80 = 280 square feet. For round rooms or features, use the formula for a circle: π × radius² (π ≈ 3.14).

How to Determine Square Footage of a Home (2026)

Accurate square footage affects your home’s value, property taxes, and listing price. Here is how to measure it yourself — and what professional appraisers actually count.

What You Need

25-foot or 50-foot tape measure (laser distance measurers are faster and more accurate — under $30 at most hardware stores)
Graph paper or a sketch app on your phone
Calculator

Step-by-Step: Measuring Your Home

Step 1: Sketch a Floor Plan

Draw a rough outline of each floor — bedrooms, living areas, hallways, closets. Label each space. Do not worry about precision at this stage; you will fill in measurements.

Step 2: Measure Each Room

Measure the interior of each space (wall to wall), rounding to the nearest half-foot:

Length × Width = Room Square Footage
Include closets and built-in storage (they count)
Measure each floor separately

Step 3: Handle Irregular Shapes

Shape	Formula	Example
Rectangle	L × W	12 × 15 = 180 sq ft
L-shape	Divide into 2 rectangles, add	(10×20) + (8×10) = 280 sq ft
Triangle (bay window, angled wall)	(Base × Height) ÷ 2	(8×6) ÷ 2 = 24 sq ft
Circle/arch	π × r²	π × 5² = 78.5 sq ft

Step 4: Add All Rooms

Sum every room, hallway, and closet on each floor. Add each floor’s total together for the whole-home figure.

Example home:

Space	Square Footage
Living room (15×20)	300
Kitchen (12×16)	192
Dining room (11×13)	143
Master bedroom (14×16)	224
Master closet (6×8)	48
Bedroom 2 (11×12)	132
Bedroom 3 (10×11)	110
Hallways (total)	85
2 Bathrooms	95
Total	1,329 sq ft

What Appraisers Count (and What They Don’t)

Professional appraisers follow the ANSI/RESNET/ICC Standard 301 (adopted widely since 2022):

Space	Counts as GLA?
Finished, heated/cooled rooms above grade	✅ Yes
Hallways, closets, stairways	✅ Yes
Finished attic (7+ ft ceiling height)	✅ Yes
Attached garage	❌ No
Unfinished basement	❌ No
Finished basement (below grade)	❌ No (listed separately)
Covered porch or sunroom (no heat/AC)	❌ No
Detached structures	❌ No

Why Accurate Square Footage Matters

Home value and listing price: Price per square foot is a primary comparison metric. A 200 sq ft error on a $300/sq ft home = $60,000 in mispriced value.
Mortgage appraisal: Lenders require an appraisal with accurate GLA. If the listed square footage is wrong, the appraisal may come in under contract price.
Property taxes: Tax assessors base assessments partly on square footage. Errors in records could mean you are overtaxed or undertaxed.
Insurance: Homeowners insurance replacement cost estimates are based partly on finished square footage. Underreporting could leave you underinsured.

Checking Existing Records

Compare your measurement to:

County tax records — often inaccurate, especially in older homes
Previous appraisal — the most reliable existing source
MLS listing history — may include below-grade space; check the methodology
Your square footage calculator — use our square footage calculator to verify room-by-room

Written by WealthVieu

WealthVieu researches and writes data-driven personal finance guides using primary sources including the IRS, Bureau of Labor Statistics, Federal Reserve, and Census Bureau.

The content on Wealthvieu is for informational purposes only and should not be considered financial, tax, or investment advice. Consult a qualified professional before making financial decisions. Full disclaimer · Editorial policy