How to Calculate Square Footage for Any Room or Space

Measure the length and width of the room in feet. Multiply the two numbers. That is your area in square feet. A bedroom that is 12 feet long and 10 feet wide has an area of 12 x 10 = 120 square feet.

If you measured in inches, divide each measurement by 12 to convert to feet first. A room that is 144 inches by 120 inches is 12 ft x 10 ft = 120 sq ft. Try the Square Footage Calculator to double-check your math.

For a triangle: Area = 0.5 x Base x Height. The height is the perpendicular distance from the base to the opposite point. A triangular alcove with a 6 ft base and 4 ft height = 0.5 x 6 x 4 = 12 sq ft.

For a circle: Area = pi x Radius^2. A round breakfast nook with a 5 ft radius = 3.14159 x 25 = 78.54 sq ft. If you know the diameter instead, divide by 2 to get the radius.

Imagine an L-shaped living room. The long section is 20 ft x 12 ft. The short section (the bump-out) is 8 ft x 6 ft. Calculate each rectangle separately: 20 x 12 = 240 sq ft, and 8 x 6 = 48 sq ft. Total area = 240 + 48 = 288 sq ft.

This divide-and-add approach works for any irregular shape. Sketch the room, draw lines to split it into rectangles or triangles, measure each piece, calculate, and add the results together.

One square foot = 0.0929 square meters. Multiply your sq ft number by 0.0929 to get sq m. One acre = 43,560 square feet. Divide your sq ft by 43,560 to get acres.

The Unit Converter handles these conversions instantly if you need to switch between systems for international listings or construction specs.

Flooring: most materials are sold per square foot. Add 10% waste factor to your calculated area when ordering. Paint: one gallon typically covers 350-400 sq ft. Divide your wall area by 375 for a good estimate of how many gallons you need.

Rental and real estate listings use gross square footage, which usually includes closets but excludes garages and unfinished basements. Know what is and is not included when comparing listings.