`C = 2 * pi * "r" `

Enter a value for all fields

The Circumference of a Circle formula, C = 2?r, 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 the 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:

          C = 2•?•r

where:

• r is the radius of the circle.
• ? is the constant (3.141592653589....)

Related Calculators:

• Circle Area -  This computes the area of a circle given the radius (A = ? r²).
• Segment Area f(r,?) - This computes the area of an arc segment of a circle given the radius (r) and angle (?)
• Segment Area f(r,h) - This computes the area of an arc segment of a circle given radius (r) and the depth (h) into the circle.
• Sector Area f(r,?)- This computes the area of a sector (pie slice) of a circle given the radius (r) and angle (?).
• Area of Annulus- This computes the area of an annulus (ring) given the inner radius (r) and outer radius (R).
• Radius -Center to a Point - This computes the radius of a circle given the center point (h,k) and any other point (x,y) on the circle.
• Circumference -  This computes the circumference of a circle given the radius (C = 2 ? r).
• Arc Lengths - This computes the length of a cord segment (arc length) on a circle given the radius (r) and angle (?)
• Circle within a Triangle -  This 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 - This computes the radius of a circle that circumscribes a triangle given the length of the three sides (a,b,c) of the triangle.
• Radius from Circumference - This computes the radius of a circle given the circumference.
• Circumference from Area - This computes the circumference of a circle given the area.
• Radius from Area - This computes the radius of a circle given the area.
• Radius from Cord-  This computes the radius of a circle based on the length of a cord and the cord's center height.