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Square Footage Calculator

Pick a shape, enter its measurements in feet and inches or any other unit, and get the area in square feet, square inches, square yards, square meters and acres. Add a quantity, a waste percentage and a price to estimate what the material will cost.

How to calculate square footage

Measure the length and the width in feet and multiply them. A room 12 feet long and 10 feet wide is 120 square feet. If a measurement includes inches, divide the inches by 12 and add them to the feet first, so 12 ft 6 in becomes 12.5 ft and a 12 ft 6 in by 10 ft floor is 125 square feet.

An L-shaped room or any other irregular space is easiest to split into rectangles. Work out each part on its own and add the results together.

Square foot formulas by shape

Square: side × side. Rectangle or room: length × width. Triangle: base × height ÷ 2, or Heron’s formula when you only know the three sides. Trapezoid and cathedral wall: (side a + side b) ÷ 2 × height. Circle: π × (diameter ÷ 2)².

A border is the outer shape minus the inner one, so a 2 ft border around a 10 ft by 8 ft rectangle covers 88 square feet. For a wall, subtract the window: a 12 ft by 8 ft wall with a 4 ft by 3 ft window leaves 84 square feet. For several identical windows, multiply the window width by how many there are.

Estimate flooring, tile or paint cost

Enter a price and the unit it is sold in. With 10% extra for cuts and breakage at $3 per square foot, a 120 square foot floor needs 132 square feet and costs $396.00.

Materials sold by the box work the same way. Enter the price of one box in Price and the area one box covers in Per, then choose the unit that coverage is measured in.