Ask a Professional: How Big Is My House in Square Feet?

Updated May 23, 2024

Having an accurate measurement is essential for appraisals and home valuation

Many aspects of building appraisal or valuation require personal judgment, but one aspect that should not fall into this category is the measurement of a house’s size. The actual size of a property is either determined from accurate building plans or by actually calculating the square footage of a house. 

An appraiser, assessor, realtor, insurance agent, or anyone who is calculating the square footage of a house should all come up with the exact same number. If you note that the sizes of your property reported from these professionals do not match, then it is time to ask some questions and/or calculate the square footage of your house yourself.

How Is the Square Footage of a Home Determined and Why Is it Important?

Square footage is one of the most important pieces of data that can be collected on a home.

• Appraisers measure and calculate square footage to be used in their appraisal; as a result, very similar sales in a given area are chosen and adjustments are made to the comparable sales based on square footage differences.

• Assessors use the square footage of your home when calculating its assessed value and thus your property taxes.

• Realtors use the square footage of your property as a tool for marketing your home.

• Insurance agents also need to know the size of your home: For insurance replacement purposes, every square foot needs to be accounted for, and of course, your insurance premium costs are will be based on the size listed.

When professionals are calculating the square footage of a house, they should all be looking at the habitable areas of the property. One term used in the industry is Total Living Area (TLA), or total finished living area that has heating, ventilation, and lighting, excluding basements. The TLA should always be calculated by square footage measurements, starting with the use of some kind of measuring device from the exterior side of the walls.

What Should Not be Included in TLA

The components above are measured and valued differently.

Basic Standards for Calculating the Square Footage of a House

The American National Standards Institute (ANSI) has standards for measuring the square footage of single-family homes. While ANSI’s standards for measuring homes are only a guide and are not law, several of these best practices for calculating the square footage of a house are listed below:

1. Measurements should be recorded to the nearest inch or tenth of a foot. The total square footage should be measured  to the nearest whole foot.
2. Since the TLA is calculated using exterior dimensions, the area of the stairs and landing are included in the square footage of both levels.
3. Where openings exist to the floor below, such as a two-story home with an open foyer, be sure to exclude that area from the square footage of that level.
4. Measure any areas below the grade and list those levels separately.
5. If a home has a finished attic, or a half-story with sloped ceilings, then standards exist how to calculate that room’s square footage. Rooms to be counted in square footage calculations should have a height of at least seven feet. If a room has a ceiling that is predominantly seven feet high, then include square footage of any floor area that is covered under a sloped ceiling that is at least five feet high.

Devices and Technologies for Calculating the Square Footage of a House

When measuring a house’s square footage, there are a variety of devices available. Years ago, 10-foot measuring sticks were used. They were quick and easy to use, but not very accurate. Wheel devices and are very efficient for measuring long distance, but results also must be checked closely and used carefully. Tape measures, which come in a variety of types and lengths, are very accurate, were known as the industry standard, and are still used today. A laser distance-measuring tool uses a laser light for very accurate measuring, so long as the device is used properly and the target is fixed on the end of the wall being measured. There are also applications for smart phones that allow the user to measure dimensions from a mobile device.

Currently, there are digital software sketching solutions available that enable mobile professionals who draw floor plans and other sketches to calculate areas from measurements they gather on site. Whatever device is chosen, there are software and apps that allow the property valuation professional to electronically sketch any building or property out in the field on mobile devices, including smart phones.

By sketching the building in the field, professionals can determine dimensions immediately and avoid the possibility of making another trip to remeasure the building. They can also add the horizontal and vertical dimensions recorded to ensure that the totals equal the overall dimensions.

All homeowners should know the square footage of their homes. This number does not change, unless the homeowner adds or removes parts of the structure. When any kind of valuation professional measures or verifies your home’s square footage, be sure you get a copy and keep it with the rest of your records.

It is in your best interest to ensure that different square footage estimates are resolved when and if there is a discrepancy. To help, CoreLogic offers a number of data-driven products for appraisal businesses. Among these is Marshall & Swift, which provides a comprehensive set of tools for accurately valuing properties and assessing replacement costs.

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