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Square Footage Calculator

Find the square footage of a rectangle, circle, triangle, trapezoid, sector, or parallelogram — plus borders and rings — and optionally price the area.

Length × width

ExampleSample values — edit any field to see your result.

How many identical shapes to include. Area is multiplied by this count.

$

Leave blank to skip cost. Converted into the unit below, then rounded to cents.

Results update as you type.

Area

600ft²

Estimated result

Result in other units

AmountUnit
0.0137741acre(s)
600ft²
66.66666667yd²
86,400in²
55.741824m²
0.00005574km²
557,418.24cm²
Area600 ft²

Estimate the square footage of a lot, room, or other surface from a common shape. Pick a tab, enter lengths in feet, yards, inches, miles, meters, kilometers, or centimeters, and optionally a unit price. Complex outlines can be split into these shapes and added together.

Formula

All lengths are converted to feet, the area of one shape is computed in square feet, then multiplied by quantity. Cost (when a price is entered) converts that area into the price unit and multiplies.

area_ft²     = shape area in feet × quantity
price        = round to cents(area in price unit × unit price)

Rectangle, parallelogram, triangle (base and height), trapezoid, and circular shapes:

rectangle        = L × W
rectangle border = L × W − max(0, L − 2b) × max(0, W − 2b)
circle           = π × (D / 2)²
ring             = π/4 × (D² − d²)     d = max(0, D − 2b)
triangle (b,h)   = (b × h) / 2
trapezoid        = ((b1 + b2) / 2) × h
sector           = (θ / 360) × π × r²   (θ in degrees)
                 = (θ / 2) × r²         (θ in radians)
parallelogram    = b × h

Three-sided triangles use Heron's formula:

s = (a + b + c) / 2
area = √(s(s − a)(s − b)(s − c))
An oversized border on a rectangle or ring is clamped so the inner opening cannot go negative — the result is then the full outer shape. Sides that cannot form a triangle (1, 1, 3) are rejected.

Area conversion factors

Factors use the international foot (1 ft = 0.3048 m exactly) and the survey acre of 43,560 ft².

UnitSquare feet
1 acre43,560 ft²
1 square yard9 ft²
1 square meter10.76391041671 ft²
1 square inch1/144 ft²
1 square centimeter0.001076391041671 ft²

Examples

30 ft by 20 ft rectangle

Length 30 ft and width 20 ft is 600 ft². At quantity 1 the result is labeled Area. Two 10 ft by 12 ft rectangles at $3 per square foot are 240 ft² and $720.

Rectangle border and ring

A 30 ft by 20 ft rectangle with a 2 ft border is 600 − 26 × 16 = 184 ft². A 30 ft diameter circle with a 2 ft ring is π(15² − 13²) = 175.92918860103 ft².

Circle, triangle, and sector

A 30 ft diameter circle is 706.8583470577 ft². A 3-4-5 triangle counted twice at $3/ft² is 12 ft² and $36. A 10 ft radius sector of 45°, quantity 2, at $3/ft² is 78.539816339745 ft² and $235.62.

1 m by 1 m at $10 per square meter

Each side is 1 / 0.3048 feet, so the area is 10.76391041671 ft². Converted back to square meters that is exactly 1 m², so the price is $10.

Frequently asked questions

How do I calculate the square footage of a rectangle?
Multiply length by width after both measurements are in the same unit. A room that is 30 ft by 20 ft is 600 square feet. This calculator converts yards, inches, miles, meters, kilometers, and centimeters to feet first, then reports the area in square feet.
How many square feet are in a square meter?
One square meter is exactly (1 / 0.3048)² = 10.76391041671 square feet, using the international foot (1 ft = 0.3048 m). A 1 m by 1 m square is therefore 10.76391041671 ft². Going the other way, 1 ft² is 0.09290304 m².
How is the optional price calculated?
The area is converted into the price unit you chose (ft², yd², in², m², or cm²), then multiplied by the unit price and rounded to the nearest cent. 240 ft² at $3 per square foot is $720. A 1 m² surface at $10 per square meter is $10, even though the area is also shown in square feet.
What is quantity used for?
Quantity multiplies the area of one shape. Two 10 ft by 12 ft rectangles are 240 ft² total. When quantity is 1 the result is labeled Area; for any other quantity it is labeled Total Area.
Can I measure an L-shaped room or an irregular lot?
Split the surface into the shapes on the tabs (rectangles, triangles, circles, and so on), calculate each piece, and add the square footages. Use Rectangle Border or Ring when you only need the frame around a rectangle or circle, such as a walkway or trim.

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