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

Divide the diameter by 2 to get the radius, then apply A = π × r².

What is the value of pi?

Pi (π) is approximately 3.14159. For most calculations, using 3.14 or 22/7 gives a close approximation.

Geometry

Area of a Circle

Formula

A = π × r²

What is Area of a Circle?

The area of a circle is the total space enclosed within its boundary. It is calculated by multiplying pi (approximately 3.14159) by the square of the radius.

Variables

A
A — Area of the circle
r
r — Radius of the circle
π
π — Pi (approximately 3.14159)

Worked Examples

Example 1

Find the area of a circle with radius 7 cm.

Solution:

A = π × 7² = π × 49 ≈ 153.94 cm²

Example 2

Find the area of a circle with radius 5 m.

Solution:

A = π × 5² = π × 25 ≈ 78.54 m²

Frequently Asked Questions

Related Formulas

Circumference of a Circle

C = 2 × π × r

Area of a Rectangle

A = l × w

Area of a Triangle

A = ½ × b × h

Pythagorean Theorem

a² + b² = c²

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