Circumference is basically the length when measured through the boundary of a circle. It is same as the perimeter of other polygons, just that it has a special name called 'circumference'. This is typically taught among basic maths calculations in schools. It is to be noted that some people falsely call circumference as circumfrence.
Circumference calculator is a free tool used to calculate the circumference of a circle when the radius is given. It can be also used to calculate other parameters of a circle such as diameter, radius and area. This means you can use this tool to do other calculations such as diameter to circumference, radius to area, radius to cicumference, area to radius, area to circumference etc. Infact, all the numbers are shown as soon as you type any one number. This is useful if you need to quickly calculate the circumference for whatever reasons.
1. Enter any one value into one of the input fields.
2. This calculator will show the results in other fields
It is quite simple. This is the equation to find the circumference when radius is given
Circumference = 2*Pi*Radius.
So, Radius = Circumference/(2*Pi)
The formula to find the circumference when radius is given is
Radius = Circumference/(2*π)
The formula to find the area when radius is given is
Area of circle = π*Radius*Radius
In the above formulas, π=3.14159 and R is the radius. You can read more about circumference in this WikiPedia article - Circumference. Or, if you are a student interested in learning more about circles, circumference, radius and their relation, then Khan Academy's this page is useful.