How to Accurately Calculate the Square Footage of Your Home

Understanding how to calculate the square feet of a house is essential whether you’re buying, selling, or renovating a home. Square footage determines property value, tax assessments, and even how much flooring or paint you need. But measuring a home’s size isn’t always as simple as it seems. Some areas count toward total square footage, while others, like garages and unfinished basements, may not. For example, in cities like San Francisco and Chicago, local building codes can influence what counts as livable space. 

This Redfin guide walks you through how to measure square footage accurately and answers common questions, like “Is a garage included in square footage?”

How is the square footage of a house calculated?

Square footage is typically measured following the ANSI (American National Standards Institute) guidelines, which provide a standardized way to calculate home size. The ANSI method requires measuring the exterior dimensions of the house, including all finished, livable spaces.

Here’s how it works:

1. Measure the exterior: Professionals measure from the outside walls to calculate total square footage. Wall thickness is included in the total but not subtracted.
2. Include finished areas: Any heated, livable space that meets height and accessibility requirements is counted. This includes main living areas, bedrooms, bathrooms, and finished attics with at least 7 feet of clearance.
3. Exclude non-livable spaces: Garages, unfinished basements, and areas requiring you to leave the main house are not included in the home’s square footage. However, finished basements may be noted separately in listings.
4. Measure each floor separately: For multi-story homes, each level’s livable space is measured and added together to determine the total square footage.

While ANSI guidelines are widely used, local real estate markets may have different rules. Always check regional regulations to ensure accurate measurements, especially when listing or appraising a home.

4 simple steps to measure the square footage of your home

Step 1: Gather your tools

To measure a home’s square footage, you’ll need:

• A measuring tape or laser distance measurer
• Pencil and paper (or a digital note-taking app)
• Calculator

A laser measurer is especially useful for large spaces and provides more precise measurements.

Step 2: Divide your home into measurable sections

Instead of trying to measure the entire house in one go, break it into smaller, rectangular sections such as individual rooms, hallways, and closets. This method minimizes errors and makes calculations easier. For non-rectangular rooms (like L-shaped areas), divide them into smaller rectangles and measure separately.

Step 3: Measure each room’s dimensions

For each room or section, follow these steps:

1. Measure the length and width in feet.
2. Multiply the length by the width to get the square footage of that section.

For example, if a bedroom is 12 feet long and 10 feet wide, the calculation is:

12 x 10 = 120 square feet

You’ll then repeat this for every section of the house.

Step 4: Add up the square footage

Once you’ve measured each section, add all the values together to get the home’s total square footage.

Example of calculating the total square feet of a house: 

What counts towards the square footage of a house?

Square footage typically includes finished, livable spaces inside the home. Here’s what usually counts and doesn’t count in official measurements:

Included in square footage of a home:

✅ Finished bedrooms, living rooms, kitchens, and bathrooms
✅ Heated and cooled areas (e.g., central HVAC or permanent heating source)
✅ Finished basements (if they meet livable space standards)
✅ Enclosed sunrooms (if heated and finished)

Not included in square footage of a home:

❌ Is a garage included in square footage? No, garages are not counted in square footage because they are not finished, livable spaces.
❌ Unfinished basements, even if enclosed
❌ Attics or lofts that don’t meet height requirements (typically at least 7 feet high)
❌ Porches, decks, and patios (unless enclosed and heated)

Check local guidelines 

If you’re selling a home, check local real estate guidelines, as definitions of “livable square footage” can vary. 

For instance, homes in Los Angeles have specific rules for measuring livable space, particularly when it comes to balconies, garages, or basements, which may not be counted in the total square footage unless they’re fully finished. NYC has stringent building codes that differentiate between “habitable” and “non-habitable” spaces, meaning certain rooms or areas might not count toward the total square footage if they don’t meet specific criteria (like windows or ceiling height). And in Seattle, the rules around livable square footage may be influenced by zoning laws and building permits, with certain areas like lofts or small upstairs rooms being counted differently from standard living spaces.

How to measure irregular-shaped homes and spaces

If your home isn’t a simple rectangle, don’t worry. You can still measure the square footage of your home, but you may have to use a few different methods.

L-shaped areas: Divide them into two rectangles, measure separately, and add their square footage.

Triangular spaces: Measure the base and height, then use the formula:

(Base×Height​)/2

Circular areas (like turrets or round rooms): Measure the diameter (the distance across the circle through its center), then divide the diameter by 2 to get the radius. Then use the formula: 

π×r2

How to measure multi-story homes

Each level should be measured separately and added together. The total square footage includes all finished areas across all floors but excludes unfinished attics and basements.

How to measure open floor plans

For open-concept spaces without clear room divisions:

1. Measure the full length and width of the open area.
2. Subtract areas not included in the livable space (e.g., stairwells, unheated sunrooms).

Why accurate square footage matters

Knowing how to measure square footage correctly is important for:

• Real estate listings: Buyers compare homes based on price per square foot.
• Home appraisals: Square footage affects property value.
• Renovations: Knowing the exact dimensions helps with materials and budgeting.
• Property taxes: Local governments assess taxes based on your home’s square footage.

Square footage plays a critical role in a home’s value, so both buyers and sellers should ensure the number is accurate. Even small discrepancies can impact home pricing, appraisals, and buyer negotiations. Here’s what each party should consider:

For sellers: avoid overstating or understating your home’s size

• Verify, don’t assume: Even if you have builder floor plans, the as-built square footage can differ from the original designs due to changes made during construction. Always measure independently or hire a professional appraiser.
• Avoid pricing pitfalls: Listing your home with incorrect square footage can lead to mispricing, which might scare off buyers if they later find discrepancies during an appraisal or inspection.
• Legal and ethical considerations: Misrepresenting square footage (even unintentionally) could lead to legal disputes or buyer demands for a lower price. Some states have disclosure laws requiring sellers to provide accurate home measurements.

For buyers: don’t rely solely on listing numbers

• Check the measurements: Real estate listings often pull square footage from tax records, which may not be updated or accurate. Ask for recent appraisals or measure the home yourself.
• Know what’s included: Some listings may include non-livable areas like finished basements, sunrooms, or enclosed patios in the total square footage. Confirm what is counted, especially in states where rules differ.
• Appraisal discrepancies can affect financing: If the appraiser measures a lower square footage than what’s listed, it could impact mortgage approval and home value assessments, leading to renegotiations.