# Circumference of a Circle

Written by Jerry Ratzlaff on . Posted in Plane Geometry

## Circumference of a Circle formulas

$$\large{ C = 2 \; \pi \; r }$$

$$\large{ C = \pi \; d }$$

$$\large{ C = 2 \; \sqrt{ \pi \; A} }$$

$$\large{ C = \frac{ 2 \; A }{ r } }$$

Symbol English Metric
$$\large{ C }$$ = circumference $$\large{ in }$$ $$\large{mm }$$
$$\large{ A }$$ = area $$\large{ in^2 }$$  $$\large{ mm^2 }$$
$$\large{ d }$$ = diameter $$\large{ in }$$ $$\large{mm }$$
$$\large{ \pi }$$ = Pi $$\large{3.141 592 653 ...}$$
$$\large{ r }$$ = radius $$\large{ in }$$ $$\large{mm }$$