This free online calculator will help you to find the area of a circle, when you know the langth of circle radius or circle diameter.

Using this online calculator, you will receive a detailed step-by-step solution to your problem, which will help you understand the algorithm how to find circle area.

Calculator

Guide

Some theory

Calculation of Circle Area

Select defined data
Input length of circle radius:
r =

Entering data into the circle area calculator

You can input only integer numbers or fractions in this online calculator. More in-depth information read at these rules.

Circle is a simple shape consisting of those points in a plane that are equidistant from a given point, the centre. The distance between any of the points and the centre is called the radius.

The formulas for calculating of circle area:

●

A = π r^{2}

●

A =

1

π d^{2}

4

where A - circle area,
r - circle radius,
d - circle diameter,
π = 3.141592.

You can input only integer numbers, decimals or fractions in this online calculator (-2.4, 5/7, ...). More in-depth information read at these rules.