Square Footage Calculator

About this tool

This square footage calculator finds the area of a room or lot from its measurements. Pick a shape, choose the unit you measured in, and enter the sizes. The result is shown in square feet, square yards, square meters and acres at the same time. For a rectangle, area is length times width. It runs in your browser and nothing is uploaded.

How to use it

Measure the longest side as the length and the shorter side as the width, then enter both. For a triangle, enter the base and the height (the straight-up distance, not the slanted side). For a circle, enter the radius, which is half of the full width. To add several rooms, calculate each one and add the square feet together. Looking for lengths only? Use the inches to mm converter or the feet to cm converter.

How to calculate square footage by hand

Measure length and width in feet and multiply. A room that is 12 feet by 15 feet is 12 times 15, which is 180 square feet. If you measured in inches, divide each side by 12 first, or multiply the inches and divide by 144. If you measured in meters, multiply by 10.764 to turn square meters into square feet.

Common room sizes in square feet

Room size	Area
10 ft x 10 ft	100 sq ft
12 ft x 12 ft	144 sq ft
12 ft x 15 ft	180 sq ft
15 ft x 20 ft	300 sq ft
20 ft x 20 ft	400 sq ft
20 ft x 30 ft	600 sq ft
40 ft x 50 ft	2,000 sq ft

Unit conversions for area

One square yard is 9 square feet, one square meter is about 10.764 square feet, and one acre is 43,560 square feet. A common mistake is to convert area the way you convert length: 1 yard is 3 feet, but 1 square yard is 9 square feet, not 3.

Where people need square footage

• Flooring, paint and tiles: you buy by the square foot, and it is wise to add about 10% for waste and cuts.
• Renting and real estate: listings, price per square foot and room comparisons.
• Lawns and gardens: fertilizer, seed and sod are sold by area covered.
• Heating and cooling: equipment sizing starts with the floor area.

Things to watch out for

Measure the real usable space and be consistent with units, since mixing feet and inches is the most common error. Rooms that are not rectangular, such as an L-shape, should be split into rectangles, calculated separately and added together. Listed square footage for homes may include walls or exclude areas such as basements, so it may not match your own measurement. Always round up when ordering materials.