In this instructable I will show you how to calculate the area of a circle

## Step 1: What You Need

You need a straightedge

a pencil (or pen whatever you want...)

a compass

a protractor and a calculator (or your mind!)

## Step 2: The Area of the Circle........well Not Really

Ok, to start you have to first find the *middle* of the circle!

(If you already know where is the middle of your circle, skip to step 3)

1st you have to draw a line anywhere around the circle. Make sure the line is outside of the circle but touching the circle (see image two). Next you have to draw a 90 degree angle using your protractor. Do this method until you find the middle (do this 3 or more times).

## Step 3: Now It's Time to Find the Area of Your Circle!

1st, draw a *precise* line with your straightedge from the middle to the edge of your circle. We will name this line "Z" but please use "r" for a test, i just like "Z" more. Next, measure the line you made.

Note: The actual abbreviation for inches is "in."

## Step 4: Calculating!

The initial calculation is "Pi Your measurement squared" or more precise, "Pi Z squared". The last thing to do is calculate it! If you want to calculate the answer on paper (without a calculator), the approximation of pie is 3.141592654...

Now you know how to calculate the area of a circle!

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## 6 Discussions

9 years ago on Step 4

Uh, are you saying the area of a circle is πr

^{2?}Reply 9 years ago on Introduction

Yes, that is the common equation.

Reply 9 years ago on Introduction

yes

10 years ago on Introduction

More commonly, 'Z' (as you have called it) is given the letter 'r' for 'radius'.

Area (A) = pi * r

^{2 }(spoken as 'pi-r-squared')

Other than this, a nice and concise instructable - 4.5 stars for you =]

10 years ago on Introduction

sorry about the unknown letters. The unknown letters in front of the examples in step 4 is the sign "pie" and the letters after the examples is a mini 2 (for the square root)

Reply 10 years ago on Introduction

Ok I fixed the problem