Area calculator.
Use this free area calculator to get fast estimates, compare scenarios, and understand the numbers with clear step-by-step context.
Use the Area Calculator.
Results update automatically as you type. No account is required.
Enter your values
About the Area Calculator
This area calculator finds the area of common 2D shapes — rectangle, triangle, circle, trapezoid, and parallelogram. Pick a shape, enter its dimensions, and the inputs update to match. Area is always measured in square units, so if your lengths are in metres the area is in square metres.
How it works
Each shape has its own formula: rectangle = length × width, triangle = ½ × base × height, circle = π × r², trapezoid = ½ × (a + b) × height, and parallelogram = base × height. The calculator selects the right one based on the shape you choose.
Reading the result
The result shows the area in square units, with the perimeter or circumference listed where it applies so you have both key measurements at once.
Note: Calculations run instantly in your browser and use exact mathematical formulas. For very large numbers, results are shown to standard floating-point precision.
FAQ
What units does the result use?
Whatever units you enter, squared. Enter centimetres and the area is in square centimetres; the calculator does not assume any specific unit.
How do I find the area of an irregular shape?
Break it into the basic shapes here, calculate each, and add the areas together. Most complex shapes can be split into rectangles and triangles.
Why is circle area π × r²?
It comes from integrating the circumference over the radius. For everyday use, just multiply pi (≈3.14159) by the radius squared.