A diameter is a line that passes through the center of the circle and then it meets the circumference of the same circle at each of its ends. This diameter is two times the length of the radius of the circle. Thus, we can simply say that the diameter of circle is naturally a straight-line segment that will pass through the center or mid-point of the circle and the endpoints of this circle lie on this region of the circumference of the circle. Also, the diameter is known as the longest chord of a circle.

This diameter can be defined as two times the length of the radius of the circle. The radius is simply the measure from the central part of the circle to its other endpoint of the circle, while the distance of the diameter is the measurement from one end of the circle to another point on the other end of the circle, thereby passing through the central part. The diameter of the circle is denoted by the letter ‘D’. Also, there are many infinite or numerous points on the circumference of a definite circle. This means that a circle can have a number of diameters, and each of these diameters measures equal length. The formula for the diameter of a circle is 2r, where r is the radius of the circle.

**What is the Symbol for Diameter?**

Φ – this is the symbol for a diameter. This is being used in the field of engineering to represent the diameter of a circle. This symbol is commonly used in many of the technical specifications and other drawings. Suppose, Φ34 mm means the diameter of the circle measures 34 mm.

**What is the Formula for the Diameter of a Circle?**

As known, that diameter is the part of a circle. Now, let us understand a few other terms before jumping into learning the formula for the diameter of the circle.

The radius (represented by ‘r’) is the length of the line segment from the central part of the circle to an endpoint on the same circle.

Circumference (represented by C) refers to the closed boundary of the circle, also known as the perimeter of the circle. We can estimate the formula of diameter from the circumference and the radius of a circle.

**Radius of Circle**

Radius is made of a line segment that is created by joining the center of the circle to the circumference of a circle or a sphere-shaped structure. The radius length of a circle remains the same from the center to any other point on this circumference of the sphere. Thus, this is actually half of the length of the diameter.

**What is Radius?**

In the geometrical study, we can define radius as the line segment that is joining the center of the circle to the circumference or to the boundary. This is a crucial part of the circles and spheres which are represented as ‘r’.

**Radius Formulas**

The radius of a circle or a sphere is calculated by using some specific formulae. Here we are discussing the radius of a sphere formula, let us check out from the section below:

The radius formula from the diameter can be represented as follows – This is the straight line that is passing through the central region and which is joining a single point from one end to another point’s end on the other side of the circle.

The diameter is thus twice the length of the radius in this case. Mathematically this can be written as – 2 × radius. This is also known as the longest chord of the circle. Also note that when the diameter of a circle is given, then the radius formula is being expressed as:

Radius = Diameter/2 or D/2 units

This was a lucid topic on the diameter and radius of circle. To know further on similar topics, you can visit Cuemath and go for an interesting hunt on maths concepts and facts.