Square Footage Calculator

Square footage is the unit nearly every flooring, painting, roofing and real-estate figure is quoted in. This calculator works out the area of a rectangle, a circle, a triangle or a trapezoid, converts your measurements to feet first so you can mix units between fields, and gives you the result in square feet along with square metres, square yards, acres and hectares.

If you know the price per square foot — for flooring, land, or a builder's rate — enter it and the total cost appears alongside the area. The price is deliberately left as a plain number with no currency attached, so the tool works the same whether you are pricing in dollars, euros, pounds, rupees or dirhams.

Choosing the right shape

Most rooms are rectangles, so length × width is usually all you need. Reach for the other shapes when the space is not a clean rectangle:

• Trapezoid is the one people miss. A room that is wider at one end than the other is a trapezoid, not a rectangle. Measure both widths and the distance between them, and the area will be smaller than simply multiplying the average width by the length — the calculator does that averaging properly.
• Circle takes the diameter, not the radius, because that is what you can actually measure across a round room or a circular patio.
• Triangle uses the perpendicular height — the straight-line distance from the base to the opposite corner — not the length of either sloping side.

For an L-shaped room, split it into two rectangles, work out each one and add them. The calculator's “how many identical areas” field multiplies one shape, so it is the wrong tool for two different rectangles — use it twice instead.

Measure twice, and measure in the middle

Rooms are rarely perfectly square even when the drawing says they are. Measure the length at both ends and the width at both sides; if the two readings differ by more than an inch or two, treat the room as a trapezoid so the error is captured rather than averaged away. Measure at floor level rather than skirting-board height, and take the figure from wall to wall, not to the edge of the carpet.

For a whole house, measure each room separately and add the results. A single measurement around the outside of the building gives you the footprint including internal and external walls, which is a larger and different number from the usable floor area.

Worked example

A room measures 15 feet 6 inches by 12 feet 3 inches. Convert to decimal feet first — 15.5 by 12.25 — and the calculator returns 189.88 square feet, or 17.64 square metres. At a flooring price of 4 per square foot, the material cost comes out at 759.50 in the same currency.

A plot 32 feet wide at the road and 28 feet wide at the back, with 90 feet between the two widths, is a trapezoid: ½ × (32 + 28) × 90 = 2,700 square feet. At the 272.25 square foot marla standard that is 9.92 marla, and the calculator shows the figure for the 250 and 225 standards too.

Square footage is not floor area

The number this calculator produces is a flat, two-dimensional area. It is what you need for flooring, paint, roof covering and land pricing. It is not the same as the built-up area or the sellable area on a floor plan, which are measured differently and may exclude or include walls, balconies and common areas according to local rules. When a listing quotes a built-up area, ask what it includes before comparing it with a square footage figure you calculated yourself.