How to Calculate Square Footage

If you’re buying a home or selling your property, knowing how to figure out square footage is an important skill. Square footage directly impacts property value, influences your tax assessment, and determines how much you’ll pay for everything from flooring to insurance.

Many homeowners and potential buyers rely on others to provide square footage measurements, often accepting whatever figure appears on a listing without question. But knowing how to calculate square feet yourself can save you money and prevent surprises during real estate transactions.

What is Square Footage?

When real estate professionals talk about a home’s square footage, they’re typically referring to the Gross Living Area (GLA). This represents the total finished, above-grade living space suitable for year-round occupancy.

The American National Standards Institute (ANSI) defines GLA as areas that are:

• Heated or cooled by the home’s main HVAC system
• Finished with walls, flooring, and ceiling treatments comparable to the main living areas
• Directly accessible from other living areas
• Above grade (meaning above ground level)

What Counts Toward Square Footage?

Finished vs. Unfinished Spaces

Only finished spaces count toward your home’s official square footage. Finished spaces typically include:

• Complete wall coverings (painted drywall, paneling, etc.)
• Finished flooring (not just subfloor or concrete)
• Finished ceilings (not exposed joists or rafters)
• Climate control from the home’s main HVAC system
• Lighting and electrical outlets

Unfinished spaces generally have:

• Exposed studs or foundation walls
• Concrete or subfloor surfaces
• Exposed beams or joists overhead
• Limited or no climate control
• Minimal electrical systems

Unfinished spaces won’t count toward your square footage until the work is completed according to local building requirements.

Rules About Basements, Attics, and Garages

Basements present one of the most common areas of confusion in square footage calculations:

• Unfinished basements never count toward a home’s official square footage total, though they may be mentioned separately in listings as additional space.
• Finished basements are handled differently depending on location. In most US markets, even beautifully finished basements don’t count toward the official square footage because they’re below grade (underground).
• In some regions, walkout basements may have portions that count if they’re at least partially above ground level.

For attics to count toward square footage:

• They must be finished to the same standards as the rest of the home.
• They need permanent, code-compliant access (typically a fixed staircase, not pull-down stairs).
• They must have ceiling heights of at least 7 feet over at least 50% of the space.
• They need proper permits and meet building codes for habitable space.
• An attic with sloped ceilings may only count partially toward square footage, typically only the areas where the ceiling height is 5 feet or higher.

Attached or detached garages rarely count toward a home’s total square footage, even if they’re finished, insulated, and heated. This remains true even for converted garage spaces unless:

• The conversion was done with proper permits.
• The space meets all local building codes for habitable areas.
• The floor has been raised to the same level as the main house (if originally lower).
• The conversion is permanent (not easily reversible).

When in doubt, consult a local real estate professional familiar with your specific market’s standards, as regional variations can significantly impact how these spaces are classified.

How to Measure Square Feet: A Room-By-Room Guide

Measuring your home’s square footage, room by room, is the most methodical approach to getting an accurate total. All you need is a measuring tape at least 25 feet long, paper, and a pencil to record measurements.

Measuring Regular Rectangular Rooms

For standard rectangular rooms:

1. Measure the length of the room from wall to wall at floor level. Be consistent when measuring from the inside edges of the walls.
2. Measure the width of the room from the opposite walls.
3. Multiply the length by the width to get the square footage.

Be sure to measure from wall to wall, not from the edges of baseboards or moldings, as you want the true interior dimensions.

Measuring Irregular-Shaped Rooms

Many homes have rooms with irregular shapes, such as:

• L-shaped rooms
• Rooms with bay windows
• Spaces with angled walls or alcoves

For these spaces:

1. Divide the room into measurable rectangles or squares. Draw a rough sketch and split the space into regular shapes.
2. Measure each section separately, calculating the square footage of each rectangular portion.
3. Add all sections together to get the total square footage.

For rooms with angled walls or odd configurations, breaking the space into triangles and rectangles often works best. Remember the formula for a triangle’s area is (base × height) ÷ 2.

Kitchens and Bathrooms

For kitchen calculations, measure the entire floor area, not just the walkable space. When measuring:

• Include the full floor space, including areas under cabinets and islands
• Measure from wall to wall, not from cabinet to cabinet
• Include connected breakfast nooks or eating areas if there’s no clear dividing wall

For bathrooms, include:

• The entire floor area from wall to wall
• Space occupied by bathtubs, showers, and toilet areas
• Built-in storage or linen closets within the bathroom

Don’t subtract space for vanities, toilets, or bathtubs—the square footage calculation includes the entire floor area, even parts covered by fixtures.

Handling Closets and Built-ins

When measuring for a home’s total square footage:

• Include walk-in closets as part of the room they’re attached to
• Include hallway closets as part of your hallway measurements
• Include built-in storage areas if they’re part of the home’s interior finished space

Measuring Hallways and Stairs

Don’t forget to include hallways in your measurements:

• Measure the length and width of each hallway
• For stairs, measure the actual footprint of the staircase on each floor
• Include landings as part of your stair measurements

Typically, you’ll count the square footage of stairs on each level they occupy, as they represent usable floor space on each floor.

How Do You Calculate Square Feet of the Whole House?

Using your room-by-room measurements:

1. Add the square footage of all rooms on each floor. Don’t forget to exclude areas that don’t count toward official square footage.
2. Verify that your totals make sense compared to the floor’s overall dimensions.

For example, if your first floor measures 40 feet × 30 feet, the maximum possible square footage would be 1,200 square feet. If your room-by-room total exceeds this, you’ve made a measurement error.

Why Accurate Square Footage Matters

Property values are often calculated on a price-per-square-foot basis, meaning even small measurement errors can represent thousands of dollars in a transaction. Your property taxes and insurance premiums depend on these figures, potentially affecting your budget for years.

Beyond the financial implications, precise measurements help you make fair comparisons between properties when house hunting, plan renovations more effectively, and ensure you’re getting exactly what you pay for.

Real estate listings must accurately represent properties, and significant square footage discrepancies can lead to disputes, contract issues, or even litigation after a sale. Rather than taking listing information at face value, knowing how to calculate square feet yourself empowers you to verify measurements, negotiate more effectively, and make truly informed decisions.

For professional guidance on property measurements, contact your local REMAX agent. We can help ensure your next property transaction is based on accurate information, because in real estate, every square foot counts.