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Key Features
Instant Calculation
Get accurate results in real time with our optimized algorithm.
Mobile Friendly
Fully responsive design. Works on all devices & screen sizes.
Privacy Focused
Your data stays on your device. We don't store any inputs.
100% Free
No hidden costs. This tool is completely free forever.
Area calculations follow a different formula for each shape — this calculator covers the four most common ones in a single tool.
Choose a shape and enter its dimensions to find its area, with the matching formula shown.
How it works
Choose a shape (rectangle, square, circle, or triangle) and enter the required dimensions — length and width for a rectangle, side length for a square, radius for a circle, or base and height for a triangle. The calculator applies the matching area formula.
- Enter shape.
- Enter length / side / radius / base.
- Enter width / height (not used for square or circle).
- Click Calculate to see your results.
Examples
A rectangle
A 10×5 rectangle has an area of 50 square units.
A circle
A circle with radius 5 has an area of about 78.54 square units (π × 5²).
Who should use it
- Checking geometry homework.
- Estimating material needed for a circular or triangular section of a project.
Industry applications
- Geometry education
- Construction and landscaping area estimates
Advantages
- Covers four common shapes in a single tool.
- Shows the specific formula used for the selected shape.
Limitations
- Limited to rectangles, squares, circles, and triangles — doesn't cover irregular or compound shapes.
Common mistakes to avoid
- Using the diameter instead of the radius when calculating a circle's area — the formula requires the radius (half the diameter).
- Mixing units between the two dimensions of a rectangle or triangle (like feet for one side and inches for the other).
Best practices
- Convert all dimensions to the same unit before entering them, to avoid an incorrect result.
Tips
- For an irregular shape, break it into rectangles, triangles, or circles you can calculate separately, then add the areas together.