Square Footage Calculator

How square footage is calculated

Square footage is area, not length. For dimensions already in feet, a rectangle is length × width, a square is side², a triangle is base × perpendicular height ÷ 2, and a circle is π × (diameter ÷ 2)². Mixed units are normalized before the area is calculated.

Multiple rooms and irregular spaces

For an L-shaped room or another simple irregular space, split the space into supported shapes and add each part as a separate area. The calculator keeps every row visible in the breakdown and sums the unrounded row areas into one total.

Square feet and common area conversions

Useful exact relationships include 144 in² = 1 ft², 9 ft² = 1 yd², 1 ft² = 0.09290304 m², and 43,560 ft² = 1 acre. The calculator uses the modern international foot, where 1 ft = 0.3048 m exactly.

Worked examples

• A 12 ft × 10 ft rectangle is 120 ft².
• A 3 m × 4 m rectangle is about 129.17 ft².
• The built-in three-room example totals 244 ft².

Feet are not square feet

Feet (ft) measure length; square feet (ft²) measure area. A single length cannot be converted directly to square feet without another dimension. Cubic feet (ft³) measure volume, so converting cubic feet to square feet also requires another dimension such as depth or height.

What this calculator does not decide

This is simple-shape geometry. It does not trace map polygons, certify residential gross living area, account for roof pitch, estimate flooring or tile quantities, add material waste, calculate paint coverage, price a project, or convert area into concrete volume.