Square Footage Calculator
Calculate square footage area (sq ft) for rooms, flooring, painting, and construction projects.
Area Summary
Measuring irregular space
Square footage is length times width for a rectangle, and everything harder is a matter of decomposition. Break an L-shaped room into two rectangles, compute each, and add. Subtract permanent obstructions such as a kitchen island or a structural column. For a circular area useπr², and for a triangle ½ × base × height using the perpendicular height.
Units are the usual source of error, because area scales with the square of length. A room 12 ft 6 in wide is 12.5 ft, not 12.6 — inches divide by 12, not 10. And one square yard is nine square feet, not three, because the conversion applies in both directions at once. Converting the measurements before multiplying avoids the whole problem.
Which square footage is meant varies by context, and the difference can be large.Gross area measures to the outside of the walls; net or usable area measures the interior. Property listings frequently quote gross, while flooring and paint quantities depend on net. For flooring in particular, add a waste allowance on top of whichever figure you use.
Frequently asked questions
How to calculate square feet of a room?
Square Footage = Room Length (in feet) × Room Width (in feet).
How do I calculate square footage?
Multiply length by width in feet. For irregular rooms, divide the space into rectangles, calculate each, and add them. Circles are pi x r^2 and triangles are half base times height. Measure at floor level rather than by the ceiling, since walls are rarely perfectly plumb.
How much extra material should I order?
Typically 10% for straightforward rectangular rooms, and 15-20% for diagonal layouts, patterned materials that need alignment, or rooms with many cuts and angles. Off-cuts are unavoidable, and having spare from the same batch matters for later repairs since dye lots vary between production runs.
How do I convert between square feet and square metres?
One square metre is about 10.764 square feet, so divide square feet by 10.764 to get square metres. Note that area conversions square the linear factor - the 3.28 feet in a metre becomes 10.764 in area, which is a common source of error.