# How Do You Use a Square-Footage Calculator?

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To calculate square footage using an online calculator, enter the length and width of the rectangle. Calculatorsoup.com and Calculator.net contain square footage calculators, with the latter one also including square footage calculators for triangles and circles.

To measure square footage for a triangle, Calculator.net requires the length of each side of the triangle. For a circle, you need to enter its radius into the calculator. A square foot is the unit of measurement for area and measures one foot long and one foot wide. The measurement is often used for building and home improvement purposes. Home sizes are expressed in square footage, as are room and lot sizes. It's essential to know the square footage of the room when buying flooring or wallpaper.

Building lot sizes are often expressed in acres. A homeowner who wants to know how large of house he can build on an acre can convert the building lot acreage into square feet using the formula of one acre equals 43,560 square feet. Retailers sometimes sell carpet in square yards rather than square feet. To determine how many square yards of carpet you need, divide the room's square feet by nine. For example, a room that measures 15 feet by 10 feet has 150 square feet or 16.67 square yards.

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