Area Calculator
Calculate area and perimeter for common 2D shapes including rectangle, square, triangle, circle, trapezoid, parallelogram, rhombus, ellipse, annulus, sector, and regular polygon.
2D shape area calculator
English search results for area calculator expect a broad 2D-shape hub, not a single formula page. This calculator keeps the simple shape-picker workflow and returns area, perimeter, and useful secondary values when the inputs define them.
| Shape group | Supported modes | Outputs |
|---|---|---|
| Quadrilaterals | Square, rectangle, parallelogram, rhombus, trapezoid, quadrilateral by diagonals | Area, perimeter, diagonal, side, or height when available. |
| Triangles | Base and height, three sides, two sides and included angle, right triangle, equilateral triangle | Area, perimeter, semiperimeter, radii, hypotenuse, or height. |
| Circles and ellipses | Circle, sector, annulus, ellipse | Area, circumference, arc length, chord, ring width, or approximate ellipse perimeter. |
| Regular polygon | Number of sides and side length | Area, perimeter, apothem, circumradius, and interior angle. |
Common formulas
A is rectangle area; l and w are length and width.
A is triangle area; b is base; h is perpendicular height.
A is circle area; r is radius.
A is trapezoid area; a and b are parallel bases; h is height.
Units and limits
Enter all lengths in one unit. The selected unit labels the result: perimeter is shown in the selected length unit and area is shown in the square of that unit.
Frequently Asked Questions
Sources and References
Calculations are based on the listed reference sources. Links open in a new tab.
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