Area of common 2D shapes — dimensions in any length unit.
A = l × w | A = s² | A = π r² | A = ½bh | A = ½(a+b)h | A = πab | A = bh
Each shape has its own dedicated formula. The most frequently used formulas are listed below. Select the shape that matches your problem, plug in the required measurements, and the calculator returns the area in square units.
A = π × r² = 3.14159265 × 7² = 3.14159265 × 49 ≈ 153.94 cm²
Result: Area ≈ 153.94 cm²
A circle with a radius of 7 cm has an area of approximately 153.94 cm². This means the circle covers roughly 154 square centimetres of flat surface. Because area scales with the square of the radius, doubling the radius to 14 cm would quadruple the area to about 615.75 cm² — a useful thing to remember when comparing sizes.
Area measures the size of a flat (two-dimensional) surface. It tells you how many unit squares fit inside a shape. A 1 m × 1 m square has an area of 1 m²; a 3 m × 4 m rectangle has an area of 12 m².
| Shape | Formula | |---|---| | Rectangle | l × w | | Square | s² | | Circle | π r² | | Triangle | ½ b h | | Trapezoid | ½ (a + b) h | | Parallelogram | b h | | Ellipse | π a b |
If you know all three side lengths (a, b, c), use Heron's Formula: first compute s = (a + b + c) / 2, then Area = √(s(s−a)(s−b)(s−c)). If you know two sides and the included angle θ, use Area = ½ × a × b × sin(θ).
One acre equals exactly 43,560 square feet. To convert an area from square feet to acres, divide by 43,560. This is commonly used in land measurement and real estate.
Measure the length and width of the room in feet (or metres). Multiply them together to get the floor area. For irregularly shaped rooms, divide the space into rectangles and triangles, calculate each section, then add the results. Always add 5–10% extra when ordering materials to account for cuts and waste.
'Area' typically refers to the 2D region enclosed by a flat shape. 'Surface area' refers to the total area of all the external faces of a 3D object, such as a cube or sphere. They use different formulas and serve different purposes.
Builders calculate floor area to estimate material quantities (tiles, carpet, concrete). Wall area determines paint or cladding needed. Roof area guides shingles or membrane requirements. Accurate area calculations prevent costly over-ordering or shortage of materials.
The calculator supports rectangles, squares, circles, triangles (base & height), trapezoids, parallelograms, and ellipses. Select your shape from the dropdown and the correct input fields and formula will appear automatically.
Yes. Simply enter your measurements in feet. The result will be in square feet (ft²), which is the standard unit for square footage used in real estate and home improvement.
For irregular shapes, break them into simpler shapes (e.g., rectangles and triangles), calculate the area of each part, and add them together. This technique is called the decomposition method.
The calculator computes area in the units you enter. If you enter dimensions in centimetres, the result is in cm². Use a unit conversion (divide by 10,000 to convert cm² to m², or multiply ft² by 0.0929 to get m²).
Area measures the space *inside* a shape (in square units), while perimeter measures the total length of the *boundary* of the shape (in linear units). Both are important in geometry but answer different questions.
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