How to find the Circumfrence of a Circle, the Quick and Easy Way!

Everybody here learned how to do this in 8th grade math, then again in geometry, but who actually remembers? Well, here's a brush up, in case you ever need to know this.

Let the Mathematics begin!!

### Teacher Notes

Teachers! Did you use this instructable in your classroom?

Add a Teacher Note to share how you incorporated it into your lesson.

## Step 1: Materials

There are a few general requirements to do this. You need:

A. A Circle or Circular object (coins, hockey puck, etc.)

B. A Ruler, cm. or in. depending on which you use.

C. A Brain, I'm afraid so...

D. A Calculator, or if you're a whiz, C.

## Step 2: Step A.

You need to locate two points, let's call them point A and point B, on opposite ends of the perimeter of the circle, as far away as they can be and still be on the edge. So that if a line went through them, it would go through the middle of the circle.

## Step 3: Step B.

Now, measure the distance between the two points, this should be fairly easy to do. Try to get it as exact as possible.

The picture below shows what you should have (kind of), you're measuring the diameter.

## Step 4: Mathematics

Now comes the Hard part. You take the measurement you just took, eg. 2 in., and multiply it by Pi (3.14), then you get the circumference of the circle, eg. 6.28, If you need help multiplying, Kiteman shows you how at https://www.instructables.com/id/How_to_Multiply/. Have fun! And don't poke your eye out on the circle!!

Participated in the

Burning Questions Round 6.5

## 2 Discussions

9 years ago on Introduction

I believe you can also use Pi x Pi to find the circumference when you have the radius.

Reply 9 years ago on Introduction

Or you could multiply the radius by 2 then by pi. Haha, we're on circles now, but we have done nothing with this kind of stuff...