Find the area of 11 common 2-D shapes.
A = π r². A circle with radius 7 cm has an area of 153.938040026 cm².
Area is the amount of flat surface inside a shape. Pick a rectangle, square, triangle, circle, ellipse, parallelogram, trapezoid, rhombus, circle sector, ring or regular polygon, enter its measurements and the calculator returns the area with the formula and conversions to square metres, feet, inches, hectares and acres.
For 3-D shapes use the Volume Calculator and Surface Area Calculator; for triangles from sides and angles see the Triangle Calculator. Property areas are in the Square Footage Calculator.
The calculator applies the standard method step by step.
| Item | Value |
|---|---|
| Formula | π r² |
| In cm² | 153.938040026 |
| Square meters (m²) | 0.015393804 |
| Square centimeters (cm²) | 153.938040026 |
| Square feet (ft²) | 0.1656975273 |
| Square inches (in²) | 23.8604439249 |
| Hectares | 1.5394e-6 |
| Acres | 3.8039e-6 |
| Shape | Area |
|---|---|
| Circle r7 | 153.938040026 cm² |
| Rectangle 5×3 | 15 cm² |
| Triangle b6 h4 | 12 cm² |
| Trapezoid 3,5,h4 | 16 cm² |
| Hexagon side 2 | 10.3923048454 cm² |
| Shape | Formula |
|---|---|
| Rectangle | l × w |
| Square | a² |
| Triangle | ½ b h |
| Circle | π r² |
| Ellipse | π a b |
| Parallelogram | b h |
| Trapezoid | ½ (a + b) h |
| Rhombus / kite | ½ d₁ d₂ |
| Sector | θ⁄360 × π r² |
| Ring | π (R² − r²) |
| Regular polygon | n s² ÷ (4 tan(π/n)) |
A = π × r². With r = 7, A = π × 49 ≈ 153.94.
Half the base times the height: A = ½ × b × h.
The average of the two parallel sides times the height: A = ½ × (a + b) × h.
A = n × s² ÷ (4 × tan(π ÷ n)), where n is the number of sides and s the side length.
1 m² = 10.7639 ft².
Area measures the surface inside a shape (square units); perimeter measures the distance around it (linear units).
It uses the standard method: circle A = π r² triangle A = ½ b h trapezoid A = ½ (a + b) h The full working and a worked example are shown on this page.
Decimal results use standard double-precision arithmetic (about 15–16 significant digits). Tools that work with whole numbers — big numbers, factors, bases, combinations — use exact integer arithmetic, so no digits are lost.
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