Math Calculators

Equation of a Circle Calculator

Write the standard-form equation of a circle from its center coordinates and radius.

Equation —

r² —

About the Equation of a Circle Calculator

The standard-form equation of a circle describes every point (x, y) that lies exactly a fixed distance (the radius) from a center point (h, k).

Formula: (x − h)² + (y − k)² = r²

This equation is derived directly from the distance formula, since every point on the circle is by definition r units from the center.