Processing...

`C = 2 * pi * "r" `

Enter a value for all fields

The **Circumference of a Circle** calculator computes* Circle * the circumference (perimeter) of a circle as a function of the radius (r).

**INSTRUCTIONS**: Choose units, and enter the following:

- (r) Radius of Circle

**Circumference (C):** The calculator returns the circumference (perimeter) of the circle in meters. However, this can be automatically converted to other length units via the pull-down menu.

The Math

The formula for the circumference or perimeter of a circle is:

where:

- r is the radius of the circle.
- π is the constant (3.141592653589....)

**Circle Area**- Computes the area of a circle given the radius**(A = π r**.^{2})**Area of Circle Arc Segment f(r,θ)**- Computes the area of an arc segment of a circle given the radius (**r**) and angle (**θ**)**Area of Circle Arc Segment Area f(r,h)**- Computes the area of an arc segment of a circle given radius (**r**) and the depth (**h**) into the circle.**Area of Circle Sector f(r,Θ)**- Computes the area of a sector (pie slice) of a circle given the radius (**r**) and angle (**Θ**).**Angle of Circle Sector f(r,h)**- Computes the angle in a circle from the radius and depth of the chord.**Area of Circle Annulus**- Computes the area of an annulus (ring) given the inner radius (**r**) and outer radius (**R**).**Radius of Circle from Center and a Point**- Computes the radius of a circle given the center point (**h,k**) and any other point (**x,y**) on the circle.**Circumference of Circle**- Computes the circumference of a circle given the radius (**C = 2 π r**).**Circle Arc Length**- Computes the length of an arc length on a circle given the radius (r) and angle (**Θ**)**Circle within a Triangle**- Computes the radius of a circle inscribed within a triangle given the length of the three sides (**a,b,c**) of the triangle.**Circle around a Triangle**- Computes the radius of a circle that circumscribes a triangle given the length of the three sides (**a,b,c**) of the triangle.**Circle Radius from Circumference**- Computes the radius of a circle given the circumference.**Circle Circumference from Area**- Computes the circumference of a circle given the area.**Circle Radius from Area**- Computes the radius of a circle given the area.**Circle Radius from Chord**- Computes the radius of a circle based on the length of a chord and the chord's center height.