Floor area is calculated using the fundamental geometric formula for rectangular spaces: **Area (sq ft) = Length (ft) × Width (ft)** This formula applies to any rectangular room or space. Both length and width must be measured in feet for the result to be in square feet (sqft). **Example:** A room measuring 12 feet long and 10 feet wide has a floor area of 120 square feet. For irregular or non-rectangular spaces, break the area into smaller rectangles, calculate each separately, and add them together. This method works for L-shaped rooms, alcoves, or any polygon that can be divided into rectangular sections. Always measure from the finished floor surface and include any recessed areas or closets within the room's footprint.