Introduction: Area of a Circle

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!


cyberpageman made it!(author)2009-09-02

Uh, are you saying the area of a circle is πr2?

bassclarinet23 made it!(author)2009-12-27

Yes, that is the common equation.

meh301 made it!(author)2009-09-03


kwah made it!(author)2009-03-12

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

Area (A) = pi * r2
(spoken as 'pi-r-squared')

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

meh301 made it!(author)2009-01-28

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)

meh301 made it!(author)2009-02-07

Ok I fixed the problem

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