Calculate the torsional constant (J or K) for various cross-sectional shapes.
Cross-Section Details
mm
Calculation Results
Enter cross-section dimensions
About this calculator
Quick Reference
JTorsional Constant
DDiameter
π3.14159...
Overview
The torsional constant is a property of a cross-section that is used in the calculation of an object's resistance to twist. For circular sections, it is identical to the polar moment of inertia.
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Pro Tips
Circular sections are the most efficient at resisting torsion.
The constant depends only on the geometry of the cross-section.
Units are typically length to the fourth power (m⁴ or mm⁴).
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Fun Facts
"The formula for a rectangular section involves a complex infinite series, often simplified to an empirical formula."
"A hollow tube can have nearly the same torsional constant as a solid shaft of the same outer diameter, while being much lighter."
"I-beams are very poor at resisting torsion despite being strong in bending."
