Area of Shapes Calculator
Every flat shape has its own area formula. Pick the shape — rectangle, square, triangle, circle or trapezoid — enter the measurements, and the calculator returns the area and the formula it used.
Your numbers
Result
- Shape
- Rectangle
- Formula used
- 5 × 4
| Step | Detail |
|---|---|
| Shape | Rectangle |
| Formula | 5 × 4 |
| Area | 20 |
The main formulas
Rectangle: base × height. Square: side². Triangle: base × height ÷ 2. Circle: π × radius². Trapezoid: (long base + short base) × height ÷ 2. The height is always perpendicular to the base.
Watch the height
In triangles and trapezoids, the height is the perpendicular distance from the base to the opposite vertex or side — not the slanted edge. Using the slanted side instead of the height is the most common mistake and overstates the area. Drop a perpendicular line to find the true height.
Composite shapes
Irregular areas are solved by splitting them into simple shapes: an "L" is two rectangles; a plot with a rounded corner is a rectangle plus (or minus) a circular sector. Work out each piece and add — or subtract the cut-outs.
Frequently asked questions
Sources
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Calculate