How to calculate square feet

Most people believe they’ll never use math again when they finish high school. Some of those people might become contractors or estimators, and if they do, they’ll discover certain things, like how to calculate square feet, that they will use pretty much every day.

Let’s look at the basics of calculating square feet and a few estimating tips and tricks you can use to make your construction math a little easier.

What Is Area, and How Do You Calculate It?

The first thing you should know about how to calculate square feet is what area is; then we can take a closer look at how to calculate it for various shapes.

Area, or surface area, as it is also known, is a unit of measure that quantifies the two-dimensional space something takes up. You can calculate the surface area of many things, like floors, walls, countertops, etc.

You calculate square feet differently depending on the shape you’re trying to calculate. Some of the more common formulas include:

Square: Side x Side

Rectangle: Side x Side

Triangle: Half Base X Height

Circle: π × Radius2

With just a handful of formulas, you can calculate the surface area of nearly anything.

Convert to Decimals

The next thing you need to know about how to calculate square feet is that you need to convert your measurements to decimals.

In North America, we often measure in inches and feet; sometimes, that means using fractions. Inches are also a little trickier because there are 12 in a foot, so you need to do a little extra calculations.

You can use a handy online table to convert fractions of inches to decimals, and then you can calculate the decimal value of inches by dividing the full inches by 12. Add the two together, and then add them to the full feet you have, and you should have the decimal linear feet you need to work with for your square foot calculation.

So, for instance, if you have 2’6 ¼”, you will divide 6 by twelve to give you 0.5 feet, and then add the decimal fraction or 0.025 together to get 0.525, which you would then add to 2’ to get a total of 2.525 feet.

Once you’ve converted all the measurements into decimals, calculate the area using the formulas above.

How to Calculate Square Feet from Square Meters

It’s not common in the United States, but sometimes you will get documents from architects or engineers who have used metric dimensions rather than English. You can still calculate square meters using the same formulas as you would calculate square feet, but you still need to convert it from square meters to square feet.

The easiest way to do this is to multiply your area in square meters by 10.7639. This will give you the area in square feet.

How to Calculate Square Feet from Irregular Shapes

In the construction world, we aren’t always dealing with simple shapes. The easiest way to calculate square feet from irregular shapes is to break them up into simpler ones.

Let’s assume you have a shape that looks like this:

There are two ways to answer the question of how to calculate square feet when you are dealing with something like this.

1. The first option is to calculate the area of the negative space in each corner of this shape and then deduct four times that area from the total area of the shape.
2. The second option when answering the question of calculating square feet from a shape like this is to break it into three rectangles: one longer one in the shape's center and two smaller ones on the sides. Calculate the area of each, and add them all together.

By breaking any larger irregular shape into simple components, you can accurately calculate the square footage of any shape you can think of.

Choose the Right Construction estimation Software

If you got into the construction business because you don’t love math and don’t want to struggle with calculations like these, then choosing the right estimating software is much more important. Bolster is the most innovative construction estimating software on the market. Contact our team to find out how we can help make your estimates and takeoffs simpler, faster, and more accurate.