Why do I need to know how to measure square footage of a room?

There are lots of reasons why you might need to calculate the square feet of your home. Some homeowners may need this information when listing a property for sale. Others may want to know the square footage of their home to dispute a tax assessment. The most popular reason, however, is to renovate the floor of a building.

It is essential to know how to work out the square footage of a room when planning on buying new flooring. Thankfully, figuring out your square footage is incredibly easy! To measure the square footage of a room, you must first find the square footage of all areas of the room you intend on installing new flooring on. This includes all nooks and crannies. Once you’ve done that, simply add each measurement together.

How to find the square footage of a rectangle

  1. Measure the width and length of the area in feet.
  2. Multiply your length and width together to get your area.

Note: If your measurements aren't in feet, convert them to feet first using our length converter.

Once you've carried out your calculation, you will have your square feet (ft2) figure. To calculate your cost of materials, simply multiply this figure by your price per square foot.


How to Find the Square Footage of a Room with Many Walls or Many Corners

Determining how to get square footage of a room with multiple walls and corners gets trickier. However, you can break the room down into multiple “boxes” (shapes with 4 corners and 4 sides), multiply the square footage of each box, then add those square footage amounts together.

For example, if you have a room that you’ve separated into 5 distinct rectangles that measure 100, 200, 300, 400, and 500 square feet, your room’s square footage would be a total of 1500 square feet.

3. What is Net Assignable Square Feet?

Net Assignable Square Feet (“NASF”) is the sum of

Net Assignable Square Feet (“NASF”) is the sum of all areas that are assigned to (or available for assignment to) an occupant for specific use. Examples of assignable space include classrooms, laboratories, offices, study areas, residential areas, general use rooms and special use rooms. These rooms are areas where people gather to accomplish a task.

A rule of thumb is if an area allows occupants to accomplish part of their institution’s mission, then it is most likely included in net assignable square feet. Examples of areas that would not be included in net assignable square feet are stairwells, hallways, elevator shafts and closets. These areas are not included in NASF because they are not assigned for occupant use.

Having an accurate measurement of NASF can help to determine the best spaces to allocate to a department. NASF can also help facility managers assess revenue for leased spaces and determine staffing needed to keep the area functioning correctly.

How to Calculate Net Assignable Square Feet

Determine your building’s net square feet. Then, subtract areas that do not have a specific, assigned use for occupants (i.e. stairs, hallways, closets etc.). This number is your net assignable square feet, because it measures all areas in your facility that people can actually use for activities on a day-to-day basis.

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:

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.

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.

How to measure for bullnose?

Measure the length of any outside edge where your tile edge would be exposed or you want framed out.  Bullnose (also called trim pieces and decorative tiles) are typically sold by the piece. To figure the quantity you have to establish the length of the trim piece (i.e. 6″ bullnose, 8″ decorative liner), then the rule is:  Your total linear length divided by the length of each piece equals your quantity needed.  

How to calculate square footage? 

It’s easy.  Follow these steps.

Measure the length in feet, Measure the width in feet. Multiply the length figure by the width figure.  This will be your total square footage for that portion of your project.  Continue to repeat this for all parts of the space that will get the same tile.   Add these together for your total square footage.

Measuring in inches works as well.  Do the math the same way, then divide by 144 to get your total in square feet. When calculating square footage account for the entire space (i.e. under vanity/cabinets).

How do I figure our square feet from meters?

One square meter equals 10.76 square feet. To calculate square feet from meters, you should multiply the number of meters by 10.76.

Choosing materials

If you are on a budget, the square footage of your room may influence your choice of flooring material. Large rooms require more materials, so you might want to consider lighter woods or composites in this case. If you would like more information on types of flooring, why not get in touch with Rhodium Floors today? Our friendly and experienced team will be happy to discuss your requirements.


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