# How to calculate the area of a circle if the diameter is given

The **diameter of a circle** is always a constant, no matter the size. It's the measurement of a straight line that connects two points on the circle and travels through the centre as well. The diameter determines the circumference of the circle. Although the area of a circle is generally calculated by the radius, which is half of the diameter, **the area can also be found directly using the length of the diameter. **

We know that the formula for the area of a circle is (Pi)(radius)(radius). We also know that Diameter = (Radius)(2).

Therefore, to** calculate the area with the diameter**, divide the diameter by 2, and follow the formula:

Area = (Pi)(Diameter/2)(Diameter/2)

For example, if the diameter is 6, you can follow the formula as such:

A= (Pi)(Diameter/2)(Diameter/2)

A=(3.14)(6/2)(6/2)

A=(3.14)(3)(3)

A=(3.14)(9)

**A=28.26 units squared**

Or, we can first find the radius, and use the formula containing the raidius. If we know that the diameter s 6, we can find the radius with the following formula: R=D/2

Therefore,

r= 6/2

r=3

We can then calculate the equation as such:

A= (Pi)(r)(r)

A=(3.14)(3)(3)

A=28.26 units squared

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- If you want to calculate the area of the radius of a circle, it's the same but the equation is: A = ? (pi) multiplied by the radius squared