How Can I Figure The Circumference Of A Circle If I Know The Diameter?


33 Answers

James FitzGerald Profile
In order to calculate this you need the correct formula. The formula for the circumference of a circle is classified as pi x Diameter. It can also be written as pi.d.

Circumference is in essence the distance or length around a circle. _, correctly pronounced like pie, is an irrational number, which means that it cannot be written as a fraction. So to be sure, a good approximation of π is 3.14 when used in particular formulas.

Pie, or pi, is essential in calculating the circumference. Make sure you know where the centre of the circle is first. You will need to find the diameter, which is a line that touches two ends of circle and the centre.

You can then use this line accordingly, or the radius, alongside with π in order to calculate the circumference. All you need to do is multiply the radius by 2 to obtain the diameter.

Other things to note in a circle include the radius, which is a line that touches an outer part of the circle and the centre. It does not make contact with more than one part of the outside. You will be able to replace diameter with this for an alternative formula. To obtain a radius you need to divide the diameter by 2 to get the radius.

There are two formulas and, bearing in mind if you take into consideration that you already know the diameter then it will be a lot simpler to do the circumference. In mathematical terms the circumference of a circle in algebra is described as:

C = π x Diameter

C = π x(2 x Radius)
Mainul Hussain Profile
Mainul Hussain answered
113.04 inch taking  pi=3.14
Katie Harry Profile
Katie Harry answered
Circumference is actually like a circle's perimeter. The formula for finding the circumference of a circle is:
C = Pi x r2
C = Circumference
pi = 3.14
r = radius

We have the diameter given to us. Radius is one half of the diameter, so:
Radius = Diameter
Radius =  28
Radius = 14 inches

Now, let's calculate the circumference:

C = Pi x r2
C = 3.14 x (14)2
C = 3.14 x 196
C = 615.4 inches -----ANSWER
Katie Harry Profile
Katie Harry answered
The formula to find the circumference of a circle is:

C = 2 x pi x r
C = circumference
r = radius
pi = 3.14

Now, we do not have the value for radius here although it is used in the formula.
So, we need to first find the radius of this circle. A radius is always half the value of the diameter, so:
radius = diameter/2
radius = 11/2
radius = 5.5 ft

Now, let's find the circumference:
C = 2 x pi x r
C = 2(3.14 x 5.5)
C = 2(17.27)
C = 34.54 ft

Therefore, the circumference of this circle is 34.54 feet.
Anonymous Profile
Anonymous answered
To find the circumference of a circle when you know the diameter.All you need to do is multiply the diameter by pi ( pi equals 3.14!!) and the you got it. GOOD LOB YOU DID IT!!!!
Formula:(example) 3.14-pi
x 2-the diameter
6.28-the circumference
Robyn Rothman Profile
Robyn Rothman answered
The classic formula to find the circumference of a circle is C=2pi r or Circumference equals 2 times pi (pi being 3.14) times the radius. The radius of a circle is one half of the diameter, so you can merely multiply the diameter by 3.14 (pi). That's your circumference.
Oddman Profile
Oddman answered
Yes, and so can you if you multiply 8 cm by Pi.
circumference = 8*3.1416 cm = 25.1328 cm
Anonymous Profile
Anonymous answered
If I make a circle with a diameter of 3 feet using 12 inch bricks how many will I need?
amber Jhon Profile
amber Jhon answered
The circumference of a circle is equal to the twice of product of constant pi and radius of the circle.

Circumference = 2 * pi * radius

Pi = 3.14

Diameter = 2 * radius

Radius = Diameter/ 2

radius = 14/2

Radius = 7 units

Circumference = 2 * 3.14 * 7 units

Circumference = 43.96 units

The required circumference of the circle is 43.96.
Anonymous Profile
Anonymous answered
I think 2 X (pie) X r = circumference. Pie is 3.14 and R is the radius which is 1/2 the diameter.
Anonymous Profile
Anonymous answered
If the diameter of a circle is 8 the circumference is 25.1327: 
  Circumference = (Diameter)(pi)
=Circumference = (8)(pi)
=Circumference = 25.1327
Michael Johnstone Profile
To find the circumference of a circle. You simply multiply Diameter (D) by Pi (the 3.1415 number) .
If you only have the radius(R) use R(Pi)^2
Meryl Hargreaves Profile
Multiply the diameter by pi (the Greek letter!)
Value approximates to 22/7 or 3.1416 or even more accurate depending on what you are given.
C= Pd or c=2Pr
(Haven't got the symbol for pi!!)

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