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Coordinate Geometry Calculators

Circle Equation Calculator

Write the standard and general form equation of a circle from its center and radius, or from center and a point on it.

Enter values

Results update as you type.

Result

Standard form

(x − 2)² + (y + 3)² = 25

General form
x² + y² − 4x + 6y − 12 = 0
Radius
5
Area
78.539816

About the Circle Equation Calculator

Write the standard and general form equation of a circle from its center and radius, or from center and a point on it.

Also known as: equation of a circle, circle standard form, center radius form, (x-h)^2+(y-k)^2=r^2.

How to use this calculator

  1. Enter center x (h), center y (k), also know and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

(x − h)² + (y − k)² = r²

Worked example

Using the values pre-filled in the calculator above:

  • Center x (h) = 2
  • Center y (k) = -3
  • Also know: Radius
  • Radius = 5

the calculator returns:

  • Standard form: (x − 2)² + (y + 3)² = 25
  • General form: x² + y² − 4x + 6y − 12 = 0
  • Radius: 5
  • Area: 78.539816