# Easily Learn how to find the Circumference of a Circle

Get the free Circumference of a Circle worksheet and other resources for teaching & understanding how to find the Circumference of a Circle

**Here’s how to measure Circle Circumference**

**Common Core Standard:**7.G.5

**Related Topics:**Area of a Circle, Area of a Semicircle, Perimeter of a Semicircle, Complementary Angles, Supplementary Angles, Vertical Angles

**What is the Circumference of a Circle Formula?**

So exactly how do you find the circumference of a circle anyway? Well, the first formula for Circle Circumference is C=(pi)(diameter). The second formula for Circle Circumference is C=2(pi)(r).The Circumference of a Circle is the all out border, or edge, of a circle. You can discover the Circumference of a Circle by utilizing either the radius or diameter across. The diameter is twice the radius of the span. The equation you use for how to discover Circumference of a Circle relies on if you know the radius or the diameter. In the event that you know the radius you will utilize the equation two times pi times radius. In the event that you know the diameter you will utilize pi times diameter.

**3 Easy Steps to find the Circle Circumference from Diameter or Radius**

- If you know the radius, you will multiply the radius times pi times two.
- If you know the diameter, you will multiply the diameter times pi.
- Double check your solution and make sure it has the correct units.

**Finding Circumference of a Circle Practice Problems Quiz**

**Watch the video explanation of our Circumference of a Circle Worksheet**

Watch our free video on **how to find a Circumference of a Circle**. This video shows how to solve problems that are on our free Circumference of a Circle worksheet that you can get by submitting your email above.

**Watch the free Circumference of a Circle video on YouTube here: Circumference of a Circle Video**

**Video Transcript:**

This video is about finding the circumference of a circle. You can get the circle circumference worksheet used in this video for free by clicking on the link in the description below.

When finding circumference of a circle there are typically two formulas that you have to use based off of the information that’s been given to you in a problem. Determining which circumference of a circle formula that you use depends on if you’re given either the radius or the diameter. Now the radius is just the distance from the middle of the circle to the outer edge of the circle and the diameter is the distance all the way across from one edge to the circle through the middle of the circle to the other edge. If you are given radius, the formula for circumference of a circle is c equals 2 pi times the radius, where r is the radius. And if you’re given diameter for circumference of a circle, you’re going to do circumference equals pi times the diameter. In the case of this example that gives us radius we’re going to take 15 because 15 centimeters is the radius and that’s going to get substituted in for r. Your formula will now be 2 pi times 15 because 15 is the radius. Then you take your circumference formula and you multiply 2 times pi times 15 and you will get 417.12 centimeters for the circumference.

Our second example it gives us diameter. The diameter in this case is 3 feet so we take 3 and we substitute it in for d. We’re going to do pi times 3 and then you take your circumference formula and you solve pi times 3, which gives you 9.42 feet. The main difference in solving for what is the circumference of circle formula that involves radius or the formula that involves diameter based on the differences that the problems may give you.

Let’s do a couple practice problems on our circumference of circle worksheet. The first problem on our circumference of a circle worksheet gives us 5 inches for the radius. I know this is the radius because it’s from the center point of the circle out to an outer edge. The circle circumference formula that we’re going to use is circumference equals 2 pi times the radius. In the case of this problem I know that the radius is 5 inches. We know r is 5. We’re going to take 5 for the radius and substitute it in for r. Now our formula is circumference equals 2 pi times 5 because the radius was 5 and then when you solve for circumference 2 times pi times 5 you get 31.42 inches for the circumference.

The second problem that we’re going to do on our circumference of circle worksheet is number four this time the problem gives us the diameter. I know this is the diameter because it goes all the way across from one side of the circle all the way to the other through the midpoint so it’s the whole length. This is going to be the diameter because I know it’s the diameter. I know that the formula is circumference equals pi times the diameter. In this case the diameter is 22 centimeters so we take 22 we substitute it in for diameter. The circumference is pi times 22 which is equal to 69.1 centimeters. You can try all the practice problems by downloading the free circumference worksheets above.

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