What is the area of a circle?
The area of a circle is the space enclosed within its boundary. It is measured in square units (e.g., cm², m²). The area depends on the length of the radius or diameter.
How to calculate the area of a circle?
You can calculate the area of a circle in two ways:
- From radius: A = π × r², where r is the radius
- From diameter: A = π × (d/2)², where d is the diameter
Enter the radius or diameter and the calculator will automatically compute the area, circumference and other values.
What is the circle area formula?
The standard formula is A = π × r². Here π (pi) is a mathematical constant approximately equal to 3.14159. The radius r is the distance from the center of the circle to any point on its edge. If you know the diameter d, the radius equals d/2.
What are some circle area calculation examples?
- Radius 5 cm: A = π × 5² = π × 25 ≈ 78.54 cm²
- Diameter 10 m: r = 10/2 = 5 m, A = π × 25 ≈ 78.54 m²
- Radius 1 m: A = π × 1² ≈ 3.14 m²
When is a circle area calculator useful?
A circle area calculator is useful in many everyday situations:
- Calculating the area of a round table, pool or trampoline
- Determining pipe cross-section area
- Computing circular garden or lawn areas
- Solving math homework problems
What is the formula for the circumference of a circle?
The circumference (perimeter) of a circle is calculated as C = 2 × π × r, or equivalently C = π × d. For a circle with radius 5 cm: C = 2 × 3.14159 × 5 ≈ 31.42 cm. Circumference is the distance around the circle, while area measures the space inside it.
What is the difference between radius and diameter?
The radius (r) is the distance from the center of a circle to its edge. The diameter (d) is the distance across the entire circle through the center. The diameter is always twice the radius: d = 2r. If you work with three-dimensional round objects, you may also need our sphere calculator for balls and domes, or the fraction calculator when working with measurements like d/2.