Get up to4 free estimates
for ANY type of Contractor near you
  • No Obligations
  • Stop Paying Too Much For Your Contractor
  • No Spam Calling
  • Screened & ID Checked Contractors only!

How to Figure Out Square Footage in a Super Easy Way!

how to figure out square footage How to Figure Out Square Footage in a Super Easy Way!

Why would anyone want to measure the square footage of something? Well, if you are a home buyer or renter knowing the square footage of a property and each room within it is crucial. The price of a home to buy or rent depends principally on the size of the property determined by the square footage. The bigger the footprint of the house, the costlier its going to be, not just to buy but also in taxes. As the right square footage of a property is so fundamental to its market value, a set of standards has been established, so measurements are uniform, and therefore properties can be accurately compared. The voluntary standards are set by the American National Standards Institute (ANSI) and are recommended by the National Association of Home Builders.

The ANSI Standard

This is the valid method of determining the square footage of a home. The measurement is taken of the exterior of the property, including the thickness of the walls. If the building is not rectangular, then each section needs to be measured separately and added to make the total. We will look at the practicalities of measurement in a moment. The areas that are considered part of the home are those that are habitable, i.e. they are finished and heated. Patios, porches, and garages are not included in the calculations. If you have a grand home with a vaulted ceiling, the empty space on the second floor is not included in the total area of the house. If it is impractical to measure the exterior of a property, the standard allows you to use internal measurements, and add the wall thickness.

All measurements taken should be rounded to the nearest 0.5 linear feet. Then the simple calculation of multiplying the length by the width of each section measured will give you a total square footage. This is then rounded off to the nearest whole number to give an ANSI standard square footage of the property. When homeowners do their own calculations, they often come up short, due to them only measuring the internal dimensions of rooms, and not including the wall thickness. Experts suggest that if you add 6 inches to take into consideration the walls of the building, then your measurements will be more accurate and closer to the building and realtor industry standards.

Figuring It Out

Calculating the square footage of a room, or a number of rooms become important when you are considering installing new flooring, or just want to get a rug that will fit. It can be great fun, and the easy math will remind you of your early school days. However, if you are unsure of your mathematical ability, there are a number of online resources that can do the calculations for you, so not to worry.


Most properties and rooms are rectangular in shape with a length and width, and this is the simplest square footage calculation. With a tape or laser measure get the length and width of the room. To keep to the standards rounds the figures to the nearest 0.5 feet. So if the length is 19ft 11 inches, that would be 20 feet, and if the width is 13ft 1 inch, that would be 13 feet. The simple multiplication of the one by the other, 20 x 13, gives you the result of 260 sq.ft. Of course, a home is not made up of just a single room. And not all rooms are rectangular. If there is a rectangular outcrop, just regard that as another box and measure in the same way and add to the total.

Conversely, if there is an indent in the room, this can be again calculated in the same way, and then subtracted from the overall square footage.


In some older properties you may find a triangular-shaped space, and measuring this is no problem at all if you have mastered rectangles. The calculation is similar to a rectangle, in that you measure the height and width, and then just divide by two.


Sometimes you may have a semi-circular bay window, or in some architect designed properties a room that is circular. This is a little trickier than for regular shapes, but not beyond the abilities of most people to calculate. If you go back to your high school days, you will probably be able to remember the formula we were taught to calculate the area of a circle – pi x r2. The square of the radius multiplied by the constant pi, which for floors are calculations can be taken as 3.147.

OK, this is about time you need to get your calculator out, as not many of us can do that math in our head. For example, if we were to measure the floor area of a semi-circular bay window, we would first have to get the radius of the window. If it is an exact semicircle, it is half the area of a full circle. So, all we have to do is measure the width and then divide by two to get the radius. Let’s say it’s 8ft, and therefore the radius will be 4ft, and the square footage of the floor area will be half that of a full circle 4 x4 x 3.147 = 50.35 divided by 2, which makes 25.18 sq.ft. Which using ANSI standards, we then round down to make 25 sq.ft.

If all this seems a bit complicated, there are lots of online floor area calculators that can work out the square footage for you. However, you will have to do the measuring yourself!

One of the most common discrepancies that arise when homeowners start measuring their property is that it does not match the square footage published by the contractor or realtor. As we discussed earlier, if the contractor and realtor are following the American National Standards Institute guidelines they will be including the width of the walls in all their calculations. This can add another 0.5 feet to any measurement you make on the internal walls of a house or apartment. If you take that into account, your calculations should not vary too much from the published measurements.