Circle Area Calculator
Calculate circle area from radius, diameter, or circumference.
Table of Contents
How to Use
- Select your input method (radius, diameter, or circumference).
- Enter the known measurement value.
- Click Calculate to find the circle area.
- View the area along with all other circle measurements.
What Is Circle Area?
The area of a circle is the amount of two-dimensional space enclosed within the circle's boundary. It is calculated using the formula A = πr², where r is the radius and π (pi) is approximately 3.14159.
The circle is one of the most fundamental shapes in geometry, and its area formula is essential in mathematics, engineering, and physics.
Circle Formulas
- Area: A = πr²
- Circumference: C = 2πr = πd
- Diameter: d = 2r
- Radius: r = d/2 = C/(2π)
Real-World Applications
Circle area calculations are used in many fields: determining material needed for circular surfaces, calculating land area, designing circular components, measuring pizza sizes, and computing cross-sectional areas in engineering.
Frequently Asked Questions
- What is the formula for circle area?
- The formula for the area of a circle is A = πr², where A is the area, π is approximately 3.14159, and r is the radius of the circle.
- Can I calculate area from diameter or circumference?
- Yes! This calculator accepts radius, diameter, or circumference as input. It automatically converts to radius and calculates the area using A = πr².
- What is π (pi) and why is it used?
- Pi (π) is a mathematical constant approximately equal to 3.14159. It represents the ratio of a circle's circumference to its diameter and is essential in all circle-related calculations.