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
Embed this calculator
Copy the code and paste it into your site or blog. Credit with a link back to Contania is included, and the height adjusts itself.
<iframe src="https://contania.app/embed/math/area-of-shapes" title="Area Calculator — square, rectangle, circle, triangle" width="100%" height="720" loading="lazy" style="border:1px solid #e5e0d8;border-radius:12px;max-width:640px"></iframe>
<script>window.addEventListener("message",function(e){if(e.data&&e.data.type==="contania:embed-height"){var f=document.querySelector('iframe[src="https://contania.app/embed/math/area-of-shapes"]');if(f){f.style.height=e.data.height+"px"}}});</script>Related calculators
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