## What Is the Radius of a Circle?

The radius of a circle is a line segment that connects the center of a circle to its perimeter or circumference. This quantity is measured for all circles and is commonly abbreviated ‘r’ or ‘r’.

The radius of a circle can be calculated using three basic radius formulas. These formulas can be used when the diameter is given, when the area is given, and when the circumference is known.

## Circumference

The circumference of a circle is the distance around a circular object. It is a common mathematical topic taught in the upper grades and above, especially in geometry.

The circle comprises many points arranged equidistant from a central point, and the distance between any two points on the circumference is called the radius. It is a fixed measurement that does not change no matter what direction you measure in.

This distance is usually measured in length units such as feet, inches, centimeters, meters, miles, or kilometers. It is used in a wide range of fields, from calculating the area of an object to estimating crop yields.

To find the circumference of a circle, you need to know its radius and diameter. If you know the diameter, then you can use the formula C = 2pr to find the circumference.

## Diameter

The diameter of a circle is the distance from one point on the surface of a circle to another point on the surface and passing through the center. It is equal to double the radius of the circle.

The radius of a circle is the distance from the center to any point on its surface. It is equal to pi times the circumference of the circle.

Ancient mathematicians discovered that the circumference of a circle is always a little more than three times the diameter of a circle. They also found that the ratio of the two is about the same, no matter the circle size.

In this article, we’ll learn the diameter of a circle and how to calculate it. We’ll also learn how to use the diameter of a circle as a variable in engineering drawings or specifications. We’ll also learn how to write the formula for the diameter of a circle.

Related Article: What Is the Radius of a Circle?

## Area

The area of a circle is the total surface space that one complete cycle of the circle covers on a two-dimensional plane. It is measured in square units like centimeters (cm), inches (in), feet (ft) or meters (m).

The formula for the area of a circle is pr2 where r is the radius and p is the value of pi. The value of p is approximately 3.14159, one of the most widely used mathematical constants.

To derive the formula, you must first see how the circle is divided into sections or shapes and organize them correctly. Once done, you can see that a parallelogram is formed from the circle. The parallelogram gradually turns into a rectangle when the process is further broken into smaller sections.

## Radius

A line segment that connects the center of a circle or a sphere to its boundary or circumference is called the radius. It is an essential part of circles and spheres, abbreviated as ‘r’.

The radius length remains from the centre to any point on the circle’s circumference. This is why a process can have multiple radii within itself—all radii are equidistant from the centre.

When the diameter of a circle is given, the radius can be calculated using the formula: (d/r)2, where d is the diameter and r is the radius. This formula can be used for any circle with a given diameter.

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