How to Calculate Diameter of a Circle

Calculating the diameter of a circle is very easy if we know the different dimensions of the circle including radius, circumference or area. Also, if you don’t have the above figures, you can still calculate the diameter of the circle provided you have to draw it. If you want to know how to calculate the diameter of a circle, follow these steps.

Table of Contents

Calculate diameter based on radius, circumference or area

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If you know the measure of the circle’s radius, double it 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 circle with a radius of 4 cm, so the diameter of the circle is 4 cm x 2, or 8 cm.

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If the circumference of the circle is known, divide it by π to get the diameter. The value of π is approximately 3.14 but it’s better to 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.

Calculate the diameter based on the figure

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

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Name the two points where the line intersects the circle “A” and “B.”

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Draw 2 other circles that intersect the old circle, one using A as the center and the other using B as the center. Make sure that these two circles intersect in the form of a Venn diagram.

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

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Measure the length of the diameter. Use a ruler for the most accurate results, or if you want to be more precise, use a digital compass. So we’re done!

Advice

Get used to using the compass. This is a very useful tool for many different purposes, including drawing the diameter of a circle as shown above. Partitioning devices (akin to compasses) are sometimes used in such 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 geometry related questions are now much less challenging than before.

Things you need

Computer
Pencil, eraser
Compass
Ruler
Digital measuring compa (optional)

Steps

Calculate diameter based on radius, circumference or area

Calculate the diameter based on the figure

Advice

Things you need

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