Square feet calculator

Square footage is length times width when both are in feet. A 12 × 10 ft room is 120 square feet, which is 11.15 square metres. For a circle, multiply π by the radius squared; for a triangle, half the base times the height.

The mistake that ruins a square-footage figure is mixing units mid-measurement — taking a room as 12 feet 6 inches and entering 12.6 rather than 12.5. Six inches is half a foot, not six tenths, and the error compounds across both dimensions. Where a room is genuinely irregular, splitting it into rectangles and adding them is more accurate than trying to average, and it is also how a flooring supplier will quote it. Alcoves, bay windows and chimney breasts each want their own small rectangle.