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`r = "C" / (2* pi)`
Enter a value for all fields
The Radius of a Circle from the Circumference calculator 
Circle computes the radius (r) of a circle based on the circumference (C).
INSTRUCTIONS: Choose units and enter the following:
- (C) The circumference (perimeter) of the circle.
Radius: The calculator returns the radius in meters. However, this can be automatically converted to other length units via the pull-down menu.
The Math / Science
The formula for the radius of a circle based on the circumference is:
r = C / 2π
where:
- r is the radius of the circle
- C is the circumference of the circle
Circle Calculators
- Circle Area - Computes the area of a circle given the radius (A = π r2).
- 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 Diameter from Area - Computes the radius and diameter of a circle from the area.
- 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.
- Chord Length: Computes the length of a chord in a circle from the radius and height.
- Circle Radius from Chord - Computes the radius of a circle based on the length of a chord and the chord's center height.
- Equation of Circle from Center and Point Coordinates - Develops the general equation of a circle based on the coordinates of the center (h,k) and any point on the circle (x,y).
- Circle with same Perimeter as an Ellipse - Computes the radius of the circle with the same perimeter of an ellipse defined by the semi-major and semi-minor axes.
- Rectangles to Cover a Circle - Computes the number of rectangles needed to minimally cover a circle based on the circle's diameter and the length and width of the rectangles.