Torsion Constant for Circle Cross-section

Torsion Constant for Circle Cross-section Formula
$J \;=\; \dfrac{ \pi \cdot d^4 }{ 32 }$ (Torsion Constant for Circle Cross-section) $d \;=\; \sqrt[4]{ \dfrac{ 32 \cdot J }{ \pi } }$
Symbol	English	Metric
$J$ (Greek symbol alpha) = Torsion Constant	$in^4$	$mm^4$
$\pi$ = Pi	$3.141 592 653 ...$	$3.141 592 653 ...$
$d$ = Diameter of the Circle	$in$	$mm$