How to calculate square footage

Measure a rectangular space

Measure between the finished surfaces of the walls and keep both measurements in the same unit. If a dimension includes inches, convert the inches to part of a foot before multiplying. Six inches equals 0.5 feet and three inches equals 0.25 feet.

A room measuring 11 feet 6 inches by 9 feet is 11.5 × 9, which equals 103.5 square feet.

Divide an irregular room into simple shapes

For an L-shaped room, sketch the floor and divide it into two non-overlapping rectangles. Calculate the area of each rectangle and add the results. This is usually easier and more reliable than trying to use every wall measurement in one formula.

For a section that should not count, such as a large open shaft or fixed void, calculate that area separately and subtract it.

Calculate a circular area

Measure the radius from the center of the circle to the outer edge. Square the radius and multiply by pi, approximately 3.1416. If you measured the full diameter, divide it by two to get the radius first.

Add a project allowance carefully

Flooring and tile projects often need extra material for cuts, pattern matching, breakage, and future repairs. The appropriate allowance depends on the material, room shape, installation pattern, and installer guidance.

Calculate the measured area first, then apply the chosen allowance. For 120 square feet with a 10% allowance, plan for 132 square feet before considering package sizes.

• Measure each dimension twice.
• Keep inches and feet consistent.
• Draw irregular sections before calculating.
• Round up to whole packages only after adding the project allowance.