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Square footage calculator

Measure rooms in feet and inches, add as many areas as you need, and get the total square feet, the extra for waste and how many boxes of material to buy.

Areas to measure

Add one line for each shape. For an L-shaped room, use two rectangles.

Material (optional)

Usually 5–10% for flooring and 10–15% for tile or diagonal layouts.

Concrete (optional)

Typical: 4 in for sidewalks and patios, 5–6 in for driveways. Uses the waste % above.

Total area

— sq ft

With waste
— sq ft
Square yards
—
Square meters
—
Boxes to buy
—
Material cost
—

1 square yard = 9 sq ft. 1 square meter = 10.764 sq ft. 6 inches = 0.5 ft.

How to calculate square feet

For a rectangle, multiply the length × width in feet. A room 12 feet long and 10 feet wide has 12 × 10 = 120 square feet. If a measurement has inches, divide the inches by 12 and add them to the feet: 10 ft 6 in = 10.5 ft.

Rooms that are not rectangles

  • L-shaped rooms: split them into two rectangles, measure each one and add them. Use one line per rectangle in the calculator.
  • Closets and hallways: add them as separate lines.
  • Areas you don't cover (a kitchen island, a fireplace hearth): calculate them apart and subtract them from the total.

Triangles, circles and concrete

Choose the shape on each line. A triangle is base × height ÷ 2, and a circle is 3.1416 × (diameter ÷ 2)². For a concrete slab, enter the thickness in inches: the calculator converts the area to cubic yards to order (area × thickness in feet ÷ 27) and to 80 lb bags (about 0.6 cubic feet each), including the waste percentage.

How much extra material to buy

Cuts, mistakes and damaged pieces mean you always need a little more than the exact area. A common rule is 5% to 10% extra for plank flooring and carpet, and 10% to 15% for tile, diagonal patterns or rooms with many corners. With a box coverage, the calculator rounds up to whole boxes.

Example

A 12 × 10 ft bedroom is 120 sq ft. With 10% waste you need 132 sq ft of flooring. If each box covers 20 sq ft, you buy 7 boxes (132 ÷ 20 = 6.6, rounded up).

Frequently asked questions

How do I convert square feet to square yards?

Divide by 9. Carpet is often sold by the square yard: 120 sq ft ÷ 9 = 13.3 square yards.

How do I calculate the square feet of walls for painting?

Multiply the perimeter of the room by the wall height, then subtract doors and windows. The painting cost calculator does it for you and also tells you how much paint to buy.

Does the square footage of a house include the walls?

The square footage of a home usually refers to the floor area, measured from the outside of the exterior walls. For materials, measure the inside of each room, which is the area you will actually cover.

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