Square Footage Calculator

US & Canada

Measure one room or add up a whole house. Rectangles, circles, triangles and four sided plots, answered in square feet and square metres together.

Your space

1.What shape is it?

2.Measurements

ft
ft

3.More than one space?

For a whole house or several beds. The total below always includes what you are typing now.

    Area

    0 square feet

    0 m² · 0 sq yd

    What you might need it for

    Unit Amount

    Flooring and paint are sold by coverage, so take this number to the relevant calculator and it will work out boxes or cans.

    The formulas

    Every one of these needs the measurements in the same unit before you multiply. That is where nearly all the mistakes come from.

    • Rectangle = length × width
    • Circle = π × (diameter ÷ 2)²
    • Triangle = base × height ÷ 2
    • Four sides, two parallel = (width A + width B) ÷ 2 × the distance between them
    • From inches = inches × inches ÷ 144

    For any shape that is not on that list, split it into pieces that are and add them together. An L shaped room is two rectangles.

    Common room sizes

    Square footage of common room sizes
    Room Square feet Square metres
    8 × 10 ft 80 7.43
    10 × 10 ft 100 9.29
    10 × 12 ft 120 11.15
    12 × 12 ft 144 13.38
    12 × 14 ft 168 15.61
    12 × 16 ft 192 17.84
    14 × 20 ft 280 26.01
    20 × 20 ft 400 37.16

    Area conversions

    Converting between area units
    From To Multiply by
    1 square foot square metres 0.0929
    1 square metre square feet 10.764
    1 square yard square feet 9
    1 acre square feet 43,560
    1 acre square metres 4,046.9
    1 hectare square metres 10,000
    1 hectare acres 2.471
    1 square square feet (roofing) 100

    Working in Canada? Plans are usually drawn in metres while flooring, paint and sod are still sold by the square foot. The calculator gives both at once so you can quote from one and buy from the other.

    Measuring without getting caught out

    • Measure the floor, not the ceiling, for flooring. Sloped ceilings and bulkheads make the two different.
    • Round up when buying, not when measuring. Keep the real number, then add the waste allowance on the material calculator.
    • Check the room is actually square. Measure both ends. Older houses are routinely an inch or two out, and it compounds across a long run of flooring.
    • A roof is bigger than the floor beneath it. Pitch adds area, so take roof measurements on the slope or apply a pitch multiplier.

    Common questions

    How do I calculate square footage?
    Multiply length by width, with both in feet. A 12 ft by 14 ft room is 168 square feet (15.6 m²). The only trap is mixing units: if one measurement is in inches, convert it first rather than multiplying feet by inches.
    How do I calculate square footage from inches?
    Multiply the two measurements in inches, then divide by 144, because there are 144 square inches in a square foot. A worktop 96 inches by 25 inches is 2,400 square inches, which is 16.7 square feet. Dividing by 12 instead of 144 is the single most common mistake here, and it leaves you twelve times out.
    How do I work out the square footage of a whole house?
    Measure each room separately and add them together. Use "Add this one and measure another" above and the running total does it for you. Work room by room rather than trying to measure the outside of the building, because exterior walls, stairwells and closets make the outside dimensions misleading.
    How do I calculate the square footage of a wall?
    Width times height, then take off the doors and windows. A standard interior door is about 21 square feet and a typical window 12 to 15, so three windows and a door is roughly 60 square feet you do not have to paint. For a room, add the four walls together and subtract once at the end.
    How do I calculate the square footage of a circle?
    Area is π times the radius squared, and the radius is half the diameter. A circle 12 ft across is 113.1 square feet. Measuring across the middle and halving it is easier and more accurate than trying to find the centre first.
    How many square feet are in a square metre?
    10.764 square feet. Going the other way, one square foot is 0.0929 square metres. The calculator shows both at once, which matters in Canada where flooring is often sold by the square foot while plans are drawn in metres.
    How many square feet are in an acre?
    43,560 square feet, or 4,047 square metres. A hectare is 10,000 square metres, which is about 2.47 acres. The calculator only shows acres once the area is big enough for them to mean anything.
    What is a square in roofing?
    A roofing square is 100 square feet. Shingles are sold by the square rather than by the square foot, so a 2,000 square foot roof surface is 20 squares. Note that is the roof surface, not the floor area underneath it, which is smaller because the roof slopes.