Circle Area Calculator

The area of a circle is calculated using the formula A = π × r², where A is the area, π (pi) is approximately 3.14159, and r is the radius of the circle.

If you know the diameter, you can use the formula A = π × (d/2)², where d is the diameter. Alternatively, divide the diameter by 2 to get the radius, then use the standard area formula.

The radius is the distance from the center of the circle to any point on its edge. The diameter is the distance across the circle through its center, which is exactly twice the radius (d = 2r).

The calculator uses JavaScript's built-in Math.PI constant for high precision. You can also choose different levels of π precision (3.14159, 3.14, or 22/7) depending on your needs.

Yes! If you know the area, you can find the radius using the formula r = √(A/π). Simply input the area value and the calculator will compute the radius automatically.

The calculator supports multiple units including millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles for length measurements, with corresponding area units.

To find circumference from area: first calculate the radius using r = √(A/π), then calculate circumference using C = 2πr. Our calculator does this automatically when you input the area.

Pi (π) is a mathematical constant that represents the ratio of a circle's circumference to its diameter. It's approximately 3.14159 and is essential for all circle-related calculations because it defines the fundamental relationship between a circle's dimensions.