How to calculate square footage?

Pretty easy math: Get out your trusty measuring tape to find a room’s length and width. Then, multiply those two numbers.

But if the room isn’t a nice, neat square or rectangle, and it’s got some outcroppings and jogs, you’ll have to get creative. Swallow your horror, realize you’ll never have to go back there and channel your inner ninth grader: Divide the room into squares or rectangles. Add all the bits and bobs together to get the size of the entire space.

Or do the math on a calculator like this one at Calculator Soup, in which you can put in the room’s shape, even if it doesn’t have corners. It also can calculate price per square foot if you need that. And, because it is 2021, you can find a laser measure app on your smartphone.

If you’re apartment hunting and just need a ballpark, use your stride. The average stride is about five feet, but that depends on so many things including height, age, terrain. Or you can also look up your shoe size and how many inches that is; e.g., a women’s 8 is about 9 feet 5 inches, a men’s 10 is about 10 feet 6 inches. Keep that number in your back pocket when you’re out and about.

Average Home Size and Square Footage Trends

As an interesting side note, houses and apartments have changed in square footage over time. In the US, the average size of a single-family home is about 2,600 square feet. In 1970, the average house size was 1,660 square feet. In 1950, the average home was 983 square feet. (An interesting side note to the interesting side note, while homes are getting larger, family size is trending smaller. In 1940, there was an average of 3.6 people per household, according to US Census data. Today, it’s about 2.5.)

Conversely, today’s apartments average about 1,015 square feet, which is slightly smaller than the 1,117 square feet in 2011. This could be because more studios and one-bedroom apartments are being built and fewer two and three-bedroom units, according to CoStar data.

For some, smaller is better. There’s less upkeep, cheaper utility bills, and potentially less clutter. Perhaps this explains the recent trend of tiny houses and micro apartments, which is in direct contrast to the larger house trend. A tiny house is 400 square feet or less, while a micro apartment is usually between 100 and 300 square feet.

So … how much square footage do you need? Depending on who is living with you, the amount of stuff you have, the size of your furniture, and your personal preference, anywhere between 100 and 2,600 square feet … more or less.

Not helpful? Okay, you’ll probably want to narrow that down a little. When trying to figure out how much space you’ll need to be comfortable in your home, here are some factors to consider:


Is There More Than One Way to Measure Square Footage?

Turns out, there are at least five. We were a little surprised as well. Here’s a simplified breakdown:

  • Walls-out method: measured from the inside and taken from architectural drawings.
  • ANSI method: measured from the exterior of the property, walls aren’t subtracted.
  • Walls-in method Total Space: includes closets, storage, and non-livable spaces.
  • Walls-in method Livable Space: excludes closets and non-livable spaces.
  • The estimating method: yes, this is a thing.

Measuring square feet is vague because no one is required to define which method they used when they attached their square footage number to the apartment listing. Wouldn’t it be nice if every apartment adhered to the same method?

Measure each room

Going room by room, measure the length and width, rounding off to the nearest half-foot.

Real estate agents often use an electronic laser distance measuring tool. If you have one, place it on a wall, aiming it directly at the wall opposite it. You will then see the square footage displayed on the device’s screen. A tape measure works well if you don’t have a laser tool.

Multiply those numbers, rounding off to the nearest square foot, then write down your measurement on your sketch. For instance, if the kitchen is 10 feet by 16 feet, the total square footage is 160 square feet.

If a room has an alcove, such as a living room with an area for a home office, measure that space separately and add it to the overall square footage of the room. The same is true for rooms with closets: measure each one by multiplying the length by width.

Accuracy of a floorplan

The Strata Plan is the legal document registered at the Land Title Office that stipulates the true square footage of a condo. Listing agents generally hire professionals to measure and to create a floorplan and gross square footage for their marketing material. Take note that professional measurers calculate square footages that are often larger than the legal strata plan. I have seen a professionally measured floorplan measure up to 50 to 200 feet larger than the legal strata plan. While these measures seek to eek out every portion of useable space, the results can at no time be used to determine the true market gross value.

If true market value in a subject building at a said floor level is $1100 per square foot then a difference of 50 to 200 square feet will have a huge impact on the investment/perceived market value.


  • Strata plan legal square footage of 1575 square feet x $1100 sqft = $1,732,500
  • Floor planner square footage of 1675 square feet x $1100 sqft = $1,842,500

A listing agent that advertises the professional measures square footage on the Multiple Listing Service must disclose this in writing at time of the showing/offering for sale.

When the buyer signs their legal paperwork at time of completion with their notary or lawyer, they are signing off on the legal strata plan and square footage; this is no time to have a surprise or conflict regarding the legal square footage of their investment.

Different Units of Measurement

Using square feet is the most common unit of measurement in American real estate. But it’s not your only option. For small projects, you might want to work in square inches. For big projects, like landscaping, square yards might make more sense. And in international real estate markets, square meters are the standard for home measurements. 

Whatever your unit of measurement, the formula is the same. Multiply the length times the width to calculate the area of square and rectangular surfaces. Just make sure you’re using the same unit of measurement for your length and width. If you’re looking for square feet, measure both distances in feet; if you’re looking for square meters, measure both distances in meters.

Think again

I’ve had customers cancel their applications to units of over 800-square feet, opting for the following 690-square-foot one bedroom unit because the layout better served their needs.

The direct entry to the living quarters, square ro

The direct entry to the living quarters, square rooms, and lack of hallway means this apartment smartly utilizes the most area for the available square footage.

Why Tenants, Homeowners, and Landlords Need to Know Square Footage

There are several reasons why tenants, homeowners, and landlords should all know how to calculate square feet:

  • Knowing the square footage of a room can help you confirm if your furniture will fit.
  • Knowing the square footage of a specific surface can help you estimate renovation costs. If you’re replacing a kitchen countertop, for example, you need to calculate the square footage of the countertop so you can get accurate quotes for the cost of the job.
  • When you know how to calculate square feet, you can make sure you order the right amount of supplies and materials. If, for example, you plan to paint a wall that’s 12 feet long by 10 feet tall, you need to find the total square footage so you know how much paint to buy.
  • Perhaps most importantly, knowing the square footage of homes and apartments helps you compare prices to find the best value. Let’s say you’re deciding between two similar apartments: Apartment A is $1,500 per month and Apartment B is $1,800 per month. Which is the better deal? Well, it depends on the square footage. If Apartment A is 500 square feet and Apartment B is 1,000 square feet, you’re getting more space for your money with Apartment B. 

Apartment Space and How You Use It

If you’re only using your apartment as a place to sleep, then a smaller micro or studio would probably suit you better than a large apartment. If you frequently entertain and love hosting dinner parties, you’ll want an apartment with a generous dining space. If your mom visits regularly from out of town and you need a place for her to stay, then you might want to consider a one or two-bedroom apartment rather than a studio.  If you work from home, consider what type of space you’ll need for your office and where you’ll want it to be located.

What to leave out

A good rule of thumb to ensure you’re taking proper measurements is to exclude space you can’t walk on or live in. These types of spaces do not count as “gross living area.”

“Someone might think, ‘If I get the measurement of my first floor and I have a two-story house, I just multiply that by two,’” Day says. However, if that first floor includes a two-story foyer, you can’t count the non-usable space.

Basements and garages, even if they are finished, don’t generally count toward total square footage. Basements are typically excluded because they are built below grade, meaning below ground level. If your state does allow basements to be included in the total square footage of a home, though, you’ll likely need an ingress and egress, or a safe way to enter and exit the basement to the outside.

Finished attic spaces — with some regulations, including ceiling heights — can count toward the total square footage of your home. If you are planning to sell your home, work with a real estate agent to craft a listing that accurately reflects your property.

Square footage is an important factor when renting

Measuring an apartment or house’s square footage helps determine its value. While knowing this information can help you decide if a property is worth the rent being charged, remember that calculating square footage is subjective.

Some landlords and real estate agents may use ANSI guidelines and some not. Certain states require square footage in every listing description while others do not. That’s why it’s up to you to figure it out yourself or hire a professional to do it for you.


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