How do I calculate the area of an irregular shape?

Break the shape into smaller regular shapes — rectangles, triangles, or circles. Calculate each area separately, then add them together. This works for L-shaped rooms, irregular garden plots, and most real-world cases.

Can I use decimal values for the measurements?

Yes. If the radius is 2.75 metres or the width is 4.5 feet, enter those exact values. The calculator handles decimals without any adjustment needed.

How is the triangle area calculated if I don't know the height?

If you know all three sides but not the height, use Heron's formula: Area = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2. Some versions of CalciHub's tool offer this as a secondary option for triangles.

Is CalciHub's Area Calculator free?

Yes, fully free. No sign-up, no ads blocking the result, and no premium tier needed.

Area Calculator

Calculate the area of common 2D shapes

Circle — Inputs

A = π × r²

Radius (r)

Unit

Result

Enter valid dimensions to calculate area

What is the Area Calculator?

Area is a measure of how much flat surface a shape covers. It comes up in practical situations all the time, how much paint to buy for a wall, how large a garden bed is, or how much flooring material a room needs. CalciHub's area calculator handles the most common shapes: rectangle, square, circle, triangle, trapezoid, and ellipse. You pick the shape, enter the measurements, and the calculator does the geometry.

How Does It Work?

Each shape has its own area formula:

Rectangle: A = length × width

Square: A = side²

Circle: A = π × radius²

Triangle: A = ½ × base × height

Trapezoid: A = ½ × (a + b) × height

Ellipse: A = π × a × b

A = area (the output)

a, b = relevant side lengths or semi-axes depending on the shape

π ≈ 3.14159

How to Use CalciHub's Area Calculator

1. Select the shape from the dropdown menu.

2. Enter the required dimensions (the fields update based on the shape you picked).

3. Choose your unit, centimeters, meters, inches, or feet.

4. Click Calculate to get the area in square units.

5. Use the result directly for material estimates or planning purposes.

Tip: When measuring a room or surface, always measure twice and use the same unit throughout, mixing centimeters and meters in the same calculation is a common mistake.

A Quick Example

A circular garden has a radius of 3.5 meters. What is its area?

Formula: A = π × radius²

= 3.14159 × (3.5)²

= 3.14159 × 12.25

= 38.48 square meters

That is roughly 38.5 m² of soil, plants, or mulch to plan for. Knowing the exact figure prevents under-ordering materials and the cost that comes with a second trip.

Frequently Asked Questions

CalciHub's area calculator supports centimetres, metres, kilometres, inches, feet, and yards. Select the unit before entering your values, and the result comes out in the corresponding square unit.

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