# How to Calculate the Diameter of a Circle: 8 Steps

## Table of contents:

Calculating the diameter of a circle is easy if you know any of its other dimensions: radius, circumference, or area. It is also possible if you only have the circle design. If you want to learn how to calculate the diameter of a circle, follow these Steps.

## Steps

### Method 1 of 2: Calculating the Diameter of a Circle Using Radius, Circumference, or Area

#### Step 1. If you know the radius of the circle, multiply by 2 to get the diameter

The radius is the distance from the center of the circle to the edge. For example, if the radius of a circle is 4 cm, then the diameter is 4 cm x 2 = 8 cm.

#### Step 2. If you know the circumference of the circle, divide by π to get the diameter

Pi (π) is equal to approximately 3, 14, but you should use your calculator to get a more accurate result. For example, if the circumference of the circle is 10 cm, then the diameter is 10 cm/π, or 3.18 cm.

#### Step 3. If you know the area of ​​the circle, divide the value by π, then find the square root and multiply by 2 to get the diameter

This Method uses the following formula to find the area of ​​the circle: A = π x r2. For example, if the circle area is 25 cm2, divide the value by π, 25 cm2/π = 7.96. Then find the square root √7.96 = 2.82 cm. To get the diameter, multiply the result by two. 2 x 2.82 = 5.64 cm. Therefore, the diameter of the circle is 5.64 cm.

### Method 2 of 2: Calculating Circle Diameter from a Drawing

#### Step 1. Draw a horizontal line inside the circle from edge to edge

Use a ruler or other straight object to do this. It can be at the top, near the bottom or in the middle.

#### Step 3. Draw two overlapping circles, one using A as the center and the other using B as the center

The circles should overlap, as in the Venn diagram.

#### Step 4. Draw a vertical line through the two points where the circles overlap

This line marks the diameter of the circle.

#### Step 5. Measure the diameter

Measure using a ruler, or for greater accuracy, use a digital caliper. Ready!

## Tips

• Familiarize yourself with using a compass. It is a very useful tool in many things, including drawing the diameter of a circle, as shown above.
• Using geometric formulas and equations becomes easier with practice. You will find that geometry questions and questions will seem less challenging with a little experience.