Content

• Steps
• Advice
• What you need

Calculating the diameter of a circle is very easy if you know the different dimensions of a circle include radius, perimeter or area. In addition, if you do not have the above figures, you can still calculate the circle as long as you draw it. If you want to know how to calculate the diameter of a circle, follow these steps.

Steps

Method 1 of 2: Calculate diameter based on radius, perimeter, or area

1. 

   If you know the radius measurement of the circle, double it up to get the diameter. The radius of a circle is the distance from the center to a point on the circle. For example, we have a radius of 4 cm, so the diameter of that circle is 4 cm x 2, or 8 cm.

2. 

   
   
   If you know the circumference of the circle, divide it by π to get the diameter. The value of π is approximately 3.14, but best of all, use a calculator to get the most accurate results. For example, the circumference of a circle is 10 cm, so the diameter is 10 cm / π, or 3.18 cm.

3. 

   
   
   If you know the area of ​​a circle, divide this value by π then divide the square root of the division to find the radius of the circle, and then multiply the radius by 2 to find the diameter. This is the opposite of the formula for calculating the area of ​​a circle, A = πr. For example, if the area of ​​a circle is 25 cm, divide 25 cm by π, then divide the square root of this division to get the radius of 2.82 cm. So the diameter is calculated by doubling the radius to 5.64 cm. advertisement

Method 2 of 2: Calculate the diameter based on the figure

1. 

   
   
   Draw a horizontal line inside the circle cutting 2 points on the circle. Use the ruler to draw straight. This line can be on the top half, bottom half or anywhere inside.

2. 

   Name the two points where the line intersects the circle "A" and "B.’

3. 

   Draw two other circles cut the old circle, one using A as the center and the other using B as the center. Make sure that the two circles intersect in a Venn diagram pattern.

4. 

   Draw a line through 2 intersections of 2 newly drawn circles. This line is the diameter of the circle we are looking for.

5. 

   Measure the diameter length. Use a ruler to get the most accurate results, or if you want more accuracy, use a digital compass. So I'm done! advertisement

Advice

• Practice using the compass to get used to. This is a very useful tool that serves a variety of purposes, including drawing the diameter of a circle as shown above. A dispenser (almost like a compass) is also sometimes used in these cases.
• Applying geometric formulas or calculations will be easier in practice. Get help from someone who specializes in circles or other shapes. You will find that questions related to geometry are much less challenging now than before.

What you need

• Computer
• Pencil, eraser
• Compass
• Ruler
• Compa digital measurement (optional)