`"radius"_"(Circle)" = sqrt(( "x" - "h" )^2 + ( "y" - "k" )^2)`

Enter a value for all fields

This Radius of a Circle calculator computes the radius of a circle given the circle's center and a point Circleanywhere on the circle. 

INSTRUCTIONS: Enter the following:

• (h) This is the X-coordinate of the circle's center
• (k) This is the Y-coordinate of the circle's center
• (x) This is the X-coordinate of the point on the circle
• (y) This is the Y-coordinate of the point on the circle

Radius: The calculator returns the radius of the circle defined by these two points. 

To compute the general form of the equation of a circle from the center point (h,k) and a point on the circle (x,y), CLICK HERE.  The general form of a circle is typically as follows:  X² + bX + Y² + dY + e = 0

The Math

Note, the radius in this calculation is simply the distance between the two points. The circle's center can be placed anywhere in the X-Y Plane. The circle in this equation is centered at the point (h,k) and the point on the circle is (x,y)

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Circle Calculators

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• 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. 
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• 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.