## How to Find the Radius from the Diameter

Finding the radius from the diameter is easy.## Question

What is the radius of the circle, with diameter 10 cm, below?## Step-by-Step:

## 1

Divide the diameter, 10 cm, by 2.

10 ÷ 2 = 5 cm

## Answer:

The radius of the circle is 5 cm.## Interactive Widget

Here is an interactive widget to help you learn about finding the radius of a circle from its diameter.## Why Is Knowing the Radius in Terms of the Diameter Useful?

Most of the properties of a circle - such as its circumference and area - can be expressed in terms of the radius or diameter. Most students remember the area of a circle with a radius**r**as: But what if you are told the diameter

**d**instead? Divide it by 2 to find the radius. If you substitute

**for**

^{d}⁄_{2}**r**, a formula for the area of a circle in terms of the diameter can be found: how to find the area of a circle using the diameter

## You might also like...

geometryfinding the area of a sector (radians)finding the radius from the circumferencefinding the radius from the area

#### Help Us Improve Mathematics Monster

- Do you disagree with something on this page?
- Did you spot a typo?

__this form__.

#### Find Us Quicker!

- When using a search engine (e.g., Google, Bing), you will find Mathematics Monster quicker if you add
**#mm**to your search term.

#### Share This Page

If you like Mathematics Monster (or this page in particular), please link to it or share it with others.

If you do, __please tell us__. It helps us a lot!

#### Create a QR Code

Use our handy widget to create a QR code for this page...or any page.