Circle Calculator

Circle geometry rules and formulas

The geometric proportions of a circle are linked via simple algebraic equations using the constant $\pi \approx 3.14159$. The radius $r$ forms the core dimension:d = 2r, C = 2\pi r, and A = \pi r^2.

Sector and arc segments are calculated by dividing the central angle $\theta$ against a full revolution ($360^\circ$ or $2\pi$ radians). Arc length is defined by $L = r\theta$, and sector area equals $A_s = \frac12 r^2 \theta$.