# Torsional Constant of a Circle

Written by Jerry Ratzlaff on . Posted in Plane Geometry

## Torsional Constant of a Circle formulas

 $$\large{ J = \frac { \pi \; r^4 } { 2 } }$$ $$\large{ J = \frac { \pi \; d^4 } { 32 } }$$

### Where:

 Units English Metric $$\large{ J }$$ = torsional constant $$\large{ in^4 }$$ $$\large{ mm^4 }$$ $$\large{ d }$$ = diameter $$\large{ in }$$ $$\large{ mm }$$ $$\large{ \pi }$$ = Pi $$\large{3.141 592 653 ...}$$ $$\large{ r }$$ = radius $$\large{ in }$$ $$\large{mm }$$