Measure the length in feet
Measure the width in feet
Multiply length × width to get square feet
If the shape is a rectangle or square: square feet = length (ft) × width (ft)
If the shape is a triangle: square feet = (base (ft) × height (ft)) ÷ 2
If the shape is a circle: square feet = π × (radius (ft))²
If the shape is an irregular area: split into rectangles/triangles/circles, calculate each, then add
If measurements are in inches: divide inches by 12 to convert to feet before calculating
If measurements are in yards: multiply yards by 3 to convert to feet before calculating
If you need to convert from square inches: square feet = square inches ÷ 144
If you need to convert from square yards: square feet = square yards × 9