#Circumference of a circle free#
However, if you're unable to remember both of the formulas, you can always manipulate the info you're given so that it fits into the formula you do remember.įeel free to play around with this online circle calculator to see how the circumference changes as the diameter and radius changes. When the radius of a circle is known, the circumference can be calculated by using a formula. Generally, it's easier to use whichever formula corresponds with the characteristics of the circle you are given.
We know that the diameter is 2 times the radius, so therefore, we can divide 17 by 2 to find the radius of 8.5 You can see that this number is actually the same one as the radius given in the previous circle, and therefore, we get the same answer when we use the C = 2 π \pi πr formula.
Another relevant aspect of circles is their circumference. It doesnt matter whether you want to find the area of a circle using diameter or radius - youll need to use this constant in almost every case. All we have to do is first change the diameter into a radius. Area of a circle (d/2) 2 Where: is approximately equal to 3.14. When we substitute "d" with 17, we find that we'll get the answer of 53.41m.Īn interesting point to note is that you can still use the other formula for finding the circumference that uses the radius. Again, referring back to the two equations we can use to calculate a circle's circumference, we find that one of them simply uses C = π \pi πd. We're given the distance across a circle through its center, which is also called the diameter of a circle. The formula for the circumference of a circle is C × d, or it can be written as C 2 × × r. In this example, we aren't given the radius.