Circle Geometry

π What is Pi?

π (Pi)

The Circle Constant

The ratio of any circle's circumference to its diameter. Regardless of size, this ratio is always π ≈ 3.14159...

If diameter = 1, then the perimeter = π

An irrational number — its decimals never end or repeat. Ancient mathematicians discovered this constant appears universally in all circles, nature, and physics.

Unit

Standard Dimensions

Radius (r)

Diameter (d)

Circumference (C)

Area (A)

cm²

Formulas appear here...

Sector & Arc

Advanced

Sector Angle (θ)

deg

Arc Length (s)

- cm

Chord (L)

- cm

Sector Area

- cm²