# What is the Formula That Relates Circumference and Radius

What is the Formula That Relates Circumference and Radius.

Need to know how to notice the circumference of a circle? Can’t remember the circumference formula? Don’t sweat it—we’ve got you covered. If you know the bore, simply plug information technology into this formula:
C=πd. Were yous given the radius, instead? No problem, merely use this formula:
C=2πr. Keep reading for everything you need to know nigh how to figure out the circumference of a circle using either the diameter or the radius. We’ve even got a circumference calculator to make things easy.

1. one

Use the formula
C = πd
to find the circumference if y’all know the diameter.

In this equation, “C” represents the circumference of the circle, and “d” represents its diameter. That is to say, you can discover the circumference of a circle but by multiplying the bore by pi. Plugging π into your estimator volition requite yous its numerical value, which is a closer approximation of 3.14 or 22/7.[i]

• Diameter means a direct line segment that passes through the center of the circle and has its endpoints on the sides of the circle.
2. 2

Plug the given value of the diameter into the formula and solve.
Check out the example problem below if y’all’d like actress practise.[2]

• Instance trouble:
You have a circle tub with a diameter of 8 feet, and y’all want to build a white fence that creates a 6-foot wide infinite effectually the tub.
• To find the circumference of the fence that has to be created, you should outset discover the bore of the tub and the fence which will be eight anxiety + 6 feet + 6 feet, which will account for the entire diameter of the tub, plus the infinite between the tub and fence.
• The diameter for your circular fence is 8 + half dozen + six, or 20 feet. Now plug it into the formula, plug π into your calculator for its numerical value, and solve for the circumference:
• C = πd
• C = π x 20
• C = 62.8 feet

1. 1

Use the formula C = 2πr to detect the circumference using the

In this formula, “r” represents the radius of the circle. Over again, you can plug π into your figurer to go its numeral value, which is a closer approximation of three.14.[3]

• A radius is whatever line segment that extends from the center of the circle and has its other endpoint on the edge of the circle.
• You might observe this is similar to the C = πd formula. That’s because the radius is one-half as long equally the diameter, so the bore can be thought of as 2r.
2. ii

Plug the given radius into the equation and solve.
For this example, let’s say you’re cutting out a decorative strip of paper to wrap around the border of a pie you’ve just made. The radius of the pie is 5 inches. To observe the circumference that you demand, but plug the radius into the equation:[4]

• C = 2πr
• C = 2π x five
• C = 10π
• C = 31.iv inches

Try it yourself! Enter a value to calculate circumference.

C
= iiπ r

• Question

What is the perimeter of a circle?

This answer was written by i of our trained team of researchers who validated information technology for accuracy and comprehensiveness.

wikiHow Staff Editor

Staff Respond

The perimeter of a circle is the same as its circumference, the distance around it. The term “perimeter” refers to the distance around any closed shape, and “circumference” applies specifically to a circle or arc.

• Question

What’southward the divergence betwixt the circumference and the bore?

This answer was written by ane of our trained team of researchers who validated it for accuracy and comprehensiveness.

wikiHow Staff Editor

The diameter is the length of a straight line drawn through the center of a circle from one side to the other. The circumference is the length all the way around the exterior of the circumvolve.

• Question

What is a circumference?

Circumference is the altitude around the perimeter of a circumvolve. It is calculated by multiplying the distance across the center (diameter) by Pi (iii.1416).

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• The radius is ever going to be one-half of the diameter.[five]

• Consider buying a scientific or graphing calculator that already has π every bit ane of the buttons. This will mean less typing for you and a more accurate answer because the π push produces an approximation to π that is much more accurate than 3.14.

• Recollect: some worksheets volition inquire to replace pi with a subside, such as 3.14 or 22/7.

Testify More than Tips

Thank you for submitting a tip for review!

• Take your fourth dimension. Remember the old adage—measure twice, cutting once.

• If y’all are stuck, ask a friend, family member, or teacher for help.

• Recall to always double-check your work because one mistake will set off all your data.

Article Summary
10

To calculate the circumference of a circle, use the formula C= pi*D where C is the circumference, D is the diameter and pi is three.14. If you have the radius instead of the diameter, multiply it by two to become the diameter. You can also use the formula for the circumference of a circle using the radius which is C equals ii pi R where R is the radius. For example, if the radius of a circle is four inches, multiply iv by 2 to get the diameter which is 8 inches. Then plug the diameter into the C equals pi times D formula. Finally, multiply pi times 8 to notice that the circumference of your circle is 25.12 inches.
To see actual examples of the circumference of a circle existence calculated, read the article!

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