How to Measure Floor Area and Calculate Square Footage

Measure floor areas easily, quickly, and accurately. The correct floor measurement results are essential for ordering materials for renovation projects, preparing sales and marketing materials for a property, and designing the furniture layout.

Blog, Floor Plans

how to measure floor area 2D floor plan measurements

By Tony Gillen Images by Celine Polden

Every home remodeler should know how to measure a room and calculate square footage accurately. Many homes have rooms of different shapes and sizes. Here are the best and simplest ways of measuring a room. You will see how to measure the floor area of a room in square feet and square meters.

What Makes Measuring Floor Area of a Room Important?

If you are a home remodeler, you want to measure floor areas of a room in such a way that you:

Save time - develop a strategy for how to measure the area of a room quickly
Get square foot or square meter areas you know are accurate
Order the exact quantities of flooring you need to do your work well
Save money because you won't over-order materials that get thrown away
Save time because you won't under-order materials, and then have to re-order extra materials to finish the job
Show your customers you are a true professional, which will encourage them to use you again, refer you to others, and write great reviews about your work quality and pricing

Every room in a house or apartment will, at some point, need new carpet or flooring. The property may have just been built, just purchased by a new owner, or suffered damage of some sort. In that case, the insurance company will expect accurate measurements and price quotes.

Your reputation for working speedily, accurately, and to budget begins with knowing the best ways on how to measure areas.

How you measure floor areas depends on their shape, and size, and if there are bay windows, walk-in closets, or other extras areas.

How to Measure a Room?

Any shaped room or part of a room is easy to measure if you follow these simple steps:

Use paper and pencil to draw the shape of the room.
Include additional spaces, such as bay windows, butler's pantry, or walk-in closets. You can add them to your main sketch or draw them as separate shapes. What matters is that you include all the floor area you need to measure.
Use a good tape measure that will give you accurate distances.
Or use a laser measure, which is especially handy if the room has long walls.
In older buildings, it may be safer to measure all four walls in case of slight irregularities.
You may also want to measure the length and breadth across the middle of the room and at the edges if the old walls look to have bowed. If there is a difference, use the longer distance.
If furniture or other obstructions is in the way of your measuring tape, move it out of the way.
If the space is large or long, have someone hold one end of the tape to keep it in place if you are not using a laser measure.

Man using a laser measure to determine square footage of a room.

How to Measure the Square Footage of Different Shaped Rooms

Differently shaped floor areas, such as square, rectangle, ellipse (oval), triangle, circle, or semicircle, and annulus, all need different formulas to calculate square footage. Each square footage formula is simple to use. Just follow these steps.

Calculate the square footage of a square or rectangular area

The area of a square room is the length of one side multiplied by itself. To be sure the room is an exact square, measure two adjoining sides.

The square footage formula for a rectangular area is the length multiplied by its width.

Here are three simple examples to explain the square footage formula using actual numbers:

If the length of the square room's walls is each 7.3 feet, then 7.3 x 7.3 (also called 7.3 squared or 7.3²) = 53.3 square feet (usually written as SF.)
If the length of the long wall is 8.3 feet and the length of the short wall is 5.1 feet, then 8.3 x 5.1 = 42.3 SF.
If the length of the long wall is 18 feet 8 inches, and the length of the short wall is 11 feet 7 inches, the easiest way to calculate total square footage is to divide the inches by 12 to give you 18.67 feet and 11.58 feet, then multiply these two numbers together to provide you with a total room area of 216.1986 SF, which you round up to 217 SF.

This floor measurement app will do the sums for you.

Calculate Floor Areas with Odd, Awkward, or Irregular Shapes

Calculate square footage for a circle area

The formula for square footage or area of a Circular Room = πR². (π is 3.14) and R is the radius of the circle. The radius is half the diameter. So, the easiest way to measure the area of a circular room is to:

Measure the diameter, then halve it. So, if the distance across the middle of the room, from wall to wall, is 7 feet, the radius is 3.5 feet.
So, 3.5 X 3.5 X 3.14 = 38.465 SF (round up to 38.5 SF.)

calculate square footage for a circle area

Calculate the square footage for a triangle area

Measure the length of the base.
Measure the height. That is, the vertical line from the base to the high point of the triangle (called the apex.)
Multiply the two numbers together and then halve your answer to give you the actual square footage of the triangle.

calculate square footage for a triangle area

Calculate the square footage of a trapezoid area the easiest way

A trapezoid-shaped area could be a bay window, for example, that has three straight sides and an opening to the room. Therefore, you have two sides parallel to each other and two other sides not parallel to each other. To calculate square footage of the floor area, you:

Measure the two lengths parallel to each other, then add them together to give you the overall length. So, if one length is 3 feet and the other is 5 feet, you get 8 feet.
Measure the distance between the two parallel lengths to give you your width, say, 2 feet 6 inches (2.5 feet.)
Multiply 8 X 2.5 and divide the answer by 2 (8 X 2.5 = 20 ÷2) = 10 SF.

calculate square footage of trapezoid area

Calculate the square footage of an oval (also called an ellipse)

This square footage formula is similar to calculating the area of a circle, but instead of just measuring the radius and squaring it, you measure two radii. Here's how:

Measure the long diameter and halve it to give the long radius.
Measure the short diameter and halve it to give the short radius.
Multiply the two radii together.
Multiply the answer by π (3.14) to get the total floor area of the oval shape.

Calculate the square footage of an annulus area

An annulus is a circular shape. The easiest way to visualize it is to think of a washer. A washer is a circular piece of metal with a hole in the middle. The solid part of the washer is the annulus.

Now let's think about rooms. For example, in an entrance hall, the owner may want a circular area in the middle of the hall filled with a floor covering of one design. They want that surrounded by an outer circle of a floor covering in a different design. That outer circle is the annulus.

The easiest way to calculate the square footage of the annulus so that you can order the right amount of different-design floor covering, is this:

Call the inner circle, Circle 1, and the outer circle, Circle 2.
Measure the diameter of Circle 1. Halve it to get the radius, then do the πR²calculation to get the area of Circle 1 in square feet.
Measure the diameter of Circle 2. Halve it to get the radius, then do the πR²calculation to get the square footage of Circle 2.
Subtract the square footage of Circle 1 from the square footage of Circle 2.

The answer is the square footage of the annulus.

How to Measure the Area of an Open Space Floor Plan and Calculate Square Footage

Some rooms in a home are made up of different shapes. A kitchen, for example, may be made up of two square shapes, such as square and a rectangle. It may also have, for example, a breakfast nook with a large semicircular bay window.

To make calculating square footage simple, all you do is:

Draw the overall shape of the room.
Divide the overall shape into the different shapes (such as one square, one rectangle, and one semicircle.)
Calculate the square footage of each area and add them together to give you the total room square footage.

How to Measure a Room and Calculate Square Meters

The easiest way is to measure the area with a metric measuring tape or laser measure instead of using an imperial measuring tape showing inches and feet.

If you only have an imperial measuring tape, you have two simple choices to convert:

Multiply the length in feet by 0.3048.
To convert square feet into square meters, multiply your SF number by 0.0929.

An easy way to convert is to use this app

Need Software to Help You Draw Floor Plans?

The RoomSketcher App is a user-friendly floor plan software you can download to your computer and tablet. Draw the shape of the room or add in the exact wall measurements you get from your laser or tape measure.

With the automatic room size function, you can easily double-check your own calculation so you are confident you have calculated square footage correctly. Get started for free, and upgrade to get all professional features.

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