Project Guide

How to Calculate Square Footage

Measure the Area
A measuring tape being used to take a measurement.

The first step to find square feet is to measure the dimensions of the area you are considering. The two dimensions to measure are length and width of the surface you need to calculate.

  • To find length, locate the longest side of the area to be measured.
  • Fix a tape measure or other measuring tool to one end of the length and extend it to the other end.
  • Record the measurement.
  • To find the width, locate the shortest side of the area to be measured. Repeat the process and then record that measurement.
Step 2: Apply the Square Footage Formula

While most of us learned how to calculate square footage in school, it may help to have a reminder of the formula.

To find square feet you have to multiply the length in feet of a figure by the width in feet. This yields a product called the area, which is expressed in square feet (or square inches if you are calculating a much smaller space, such as a dollhouse, for example).

L x W = A

For example, if you are buying carpet for a room that is 12 feet long and 10 feet wide, multiply the two dimensions.

12 ft x 10 ft = 120 sq. ft.

Account for Odd Dimensions

Occasionally you may have to account for odd room dimensions or additional areas that are not contiguous with your initial calculation. In this case, to calculate the square footage accurately, you may need to divide the space into separate areas.

Measure each area separately and calculate the square footage of each individual piece. Then add the calculations together to get the total square footage.

For example, assume you are trying to buy flooring for a T-shaped space. The shape is formed of a center rectangle and two square areas. 

Find the length and width of each section, then calculate each square footage:

A: 8 ft. x 12 ft. = 96 sq. ft. 

B: 4 ft. x 2 ft. = 8 sq. ft.

C: 4 ft. x 2 ft. = 8 sq. ft.

Then, add the three values together to get the total square footage you’ll need:

96 + 8 + 8 = 112 sq. ft.

Therefore, you’ll need 112 sq. ft. of flooring materials.

Adjust for Waste

Once you’ve found the quantity of material you need to have to complete your project, be sure to adjust the amount for waste. This doesn’t mean that you are planning to waste the materials, but mistakes can happen. If you accidentally break tiles or spill paint and you have only the exact amount you needed, you may find yourself scrambling to replace your materials. Or worse, in the case of some materials, you may find yourself unable to get an exact color match with the first batch you ordered.

For this reason, order 5 to 10 percent more of your materials than you have calculated. This way you’ll be able to ensure you're covered. Materials like tile can often be returned if they haven’t been opened or used, so that you can recover a little of your extra cost once the project is complete. However, you may find it helpful to store the extra materials, in case you need to replace tiles, patch carpet or touch up paint down the road. 

Though learning how to calculate square footage is not difficult, there are shortcuts to the process. There are online square footage calculators that can help you determine your measurements and also use the measurements to help you estimate the amount of various materials you may need for projects such as landscaping or flooring.