How do you find the area of a circle?

Multiply π (pi, approximately 3.14159) by the square of the radius: A = πr².

How do you find the area if you know the diameter?

The radius is half the diameter. So A = π × (d/2)² = πd²/4.

Free Circle Area Calculator

Calculate the area of a circle from its radius. Also shows the diameter, circumference, and other circle properties.

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Radius

Area

78.5398

Circumference31.4159

Diameter10.0000

View formula & how it works →

How to Calculate the Area of a Circle

Formula

A = π × r²

Where:

A = Area

π ≈ 3.14159

r = radius

The area is the space enclosed within the circle.

Example Calculation

Find the area of a circle with radius 5.

01A = π × 5²
02= π × 25
03= 3.14159 × 25
04≈ 78.5398

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