How to calculate square feet
Multiply the length by the width, both in feet. A 14 by 12 foot room is 14 × 12 = 168 sq ft.
Feet and inches
Turn the inches into part of a foot first by dividing them by 12. Eight feet 6 inches is 8.5 feet, so a 10 foot by 8' 6" room is 10 × 8.5 = 85 sq ft. The calculator takes feet and inches as they read off the tape, including fractions such as 6 1/2.
Rooms that are not rectangles
Split the room into shapes that are. An L-shaped room is two rectangles, measured one at a time and added. An angled wall leaves a triangle; a round bay or a turret is part of a circle. Each one goes in as its own area.
The formulas
Rectangle = length × widthTriangle = base × height ÷ 2Circle = 3.1416 × (diameter ÷ 2)²To convert: one square yard is 9 sq ft, one square meter is 10.764 sq ft, and an acre is 43,560 sq ft.
Waste for materials
- Flooring and tile: about 10% extra for a straight lay, about 15% for diagonal and herringbone patterns, which cut more at the walls.
- Carpet: rolls are usually 12 or 15 feet wide, so the seams and the layout decide the order more than the area does.
- Paint and drywall go by wall area, not floor area. The drywall calculator works out the walls of a room from its size and height.
Common questions
How many square feet is a 12 by 12 room?
144 sq ft. A 10 by 10 room is 100 sq ft and a 12 by 15 room is 180.
How is a house's square footage measured?
Appraisers in the US follow the ANSI Z765 standard: finished area measured to the outside of the exterior walls, with finished space above grade and below grade reported apart, and garages left out. For flooring or paint, measure the inside of each room instead.
Do closets count?
For a flooring order, yes. Measure each closet as its own area and add it. For a house's finished square footage, closets inside finished rooms are part of the finished area.
How many square feet are in a square yard?
Nine. A square yard is 3 feet by 3 feet. Divide square feet by 9 for square yards.