How to Calculate a Home’s Square Footage

How to calculate square feet

To calculate an area in square feet, you will need measurements for the width and length (for a square shape) or the diameter (for a circular area). It may be that the area you're looking to measure is a strange shape (such as a room or garden). In this case, dividing it up into smaller parts and doing individual calculations is a good way to calculate the overall square footage.

Let's say you have a rectangular-shaped room and you want to calculate the square footage area for flooring or carpet. The easiest method for calculating the square footage is to measure the length and width in feet and then multiply the two figures together to give you a result in ft2. If you're measuring a room for flooring, take a look at our article on how to measure for a new floor.

Should you find yourself needing to calculate an area of square feet in an 'L' shape, consider dividing the shape up into rectangular sections and treating them as separate areas for calculation (adding them together at the end). For more instructions, see our full article: how to calculate square footage.

How many square feet is a 20×20 room?

The square footage of a room measuring 20 feet wide by 20 feet long is 400 square feet. To calculate this you simply multiply the width by the height. 20ft × 20ft = 400 sq ft.

Video

How to figure square footage of a wall?

It doesn’t matter whether you’re thinking how to calculate wall square footage for paint or for wallpaper – it’s the same. Use these pieces of advise to improve your ability to figure out the square feet of your wall:

Precise measurement is the key 🔑 – no matter if you’re using the wall sq ft calculator or computing everything yourself:

  • Start with drawing a plan of your room/house – it’ll make it easier to measure and store data;

  • Alway use the proper equipment – a steel tape measure or a yardstick;

  • Measure the length of your walls, including both doors and windows; and

  • Determine the height of your walls – measure them from the floor to ceiling. Exclude the length of a dropped ceiling or moulding (coving).

It’s math time! Let’s find out how to calculate the square feet of a wall.

So how do we calculate the square feet of a wall? The equation is simple:

walls square footage = total length of the walls * ceiling height

But how to calculate sq ft of a wall with doors and windows? 🤔

corrected wall square footage = wall square footage - windows area * number of windows - door area * number of doors

Now it’s time to figure out the square feet of windows and doors – take a look at the standard sizes, presented in the table below:

Windows3 x 4 ft12 ft²
Doors3 x 7 ft21 ft²

That’s how to calculate square feet of a wall. Are you still at the beginning of your journey, not yet sure about the number of planned doors and windows? Try our basic construction calculators:

How to calculate the square footage of a house

When preparing to measure the square footage of a home, be it a house, condo, or townhouse, start with a few simple supplies:

  • Paper and pencil
  • Calculator
  • Measuring tape and/or laser measuring tool

If the property is a perfect rectangle, simply measure the length and width and multiply those two numbers together. For example, if your one-story house is 60 feet wide by 40 feet long, then your property is 2,400 square feet (60 x 40 = 2,400).

However, most properties have more complex floor plans. When this is the case, it’s helpful to follow these simple steps to measure square footage.

  1. Draw a rough sketch of your entire space, labeling all of the rooms you need to measure. Include hallways and vestibules as their own “room.”
  2. Measure the length and width, in feet, of each room. Then, multiply the length by the width to calculate that room’s square footage. For example: If a bedroom is 12 feet by 20 feet, it is 240 square feet (12 x 20 = 240). For each room, write the total square footage in the corresponding space on your sketch.
  3. Once each room is measured, add up all the measurements to determine your home’s total square footage.

Note If you live in a tract home, condo or townhome community, you may be able to get architectural drawings or master builder plans of your floor plan. These may already have your square footage calculated.

How much to allow for waste?

To allow for waste, you must consider the installation.  For most standard installations, 10% extra for waste is sufficient.  Percentage of waste for more elaborate patterns like running tile on a 45 degree angle, herringbone or cross hatch, consult with your installer. Add 15% for tile being installed in a room with lots of jogs and corners. These installations will require more cuts and thus more waste.

Length x Width + Waste = Amount Needed

How to calculate how many pieces of bullnose you will need?

If you have ten feet exposed edge that needs bullnose this is equal to 120″.  If you selected a 6″ bullnose or trim piece, you will need to divide 120″ by 6″, which will give you 20 pieces of bullnose needed.  Using 8″ decorative liner for the same 120″, you divide 120″ by 8″ which would be 15 pieces of liner needed.

Wall Square Footage Calculator – Example

We will now show you one example to better understand. We will take simple numbers so that you can remember them more easily. As we said:

  • we choose the shape (for our example it is square);
  • then enter the height of the wall (5 m);
  • ceiling height (7 m);
  • number of doors (4);
  • number of windows (3);
  • and the result is printed by {wall\ footage}=128.85 \;m^2

When in doubt, ask the pros

If calculating the square feet of your particular property feels overwhelming, consider hiring a professional appraiser to do it. The average appraisal cost for a single-family home typically runs about $350. A condo appraisal fee is generally between $300 and $500, and multi-family home appraisals can run anywhere from $600 to $1,500.

While two different professional appraisers could evaluate the same home and come up with slightly different square footage figures, they do all aim for scientific accuracy. “We’re always shooting for somewhere between 1 to 3 percent variance,” Day says.

Paint Calculation Formula

Now that you’ve determined the room’s square footage, it’s a bit easier to figure out how much paint to buy. One gallon of paint typically covers 400 square feet with one coat of paint. Many wall-painting jobs require at least two coats of paint, especially if the new wall color is significantly different from the old. The paint calculation formula is as easy as determining how many gallons of paint are needed for one coat on the walls in the room. One gallon of paint is often enough for a tiny space such as a half-bath, while 2 gallons is enough to paint another coat or to paint a medium-sized room.

If the room has 500 square feet of wall space, for instance, buy 2 gallons of paint to apply one coat to the walls, which will leave enough left over for almost a full second coat.

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