🔗 Torsional Stiffness Calculator
Calculate a shaft’s torsional stiffness from shear modulus, polar moment of inertia, and length.
1
GPa
2
mm⁴
3
mm
Torsional Stiffness of a Shaft
Torsional stiffness measures how much torque is required to twist a shaft by a given angle. It’s calculated as kt = GJ / L, where G is the material’s shear modulus, J is the shaft’s polar moment of inertia (torsional constant), and L is the shaft’s length.
A stiffer (higher kt) shaft twists less under the same torque — important in drivetrains, springs, and rotating machinery where excess twist can cause misalignment or vibration. Torsional stiffness increases with a larger cross-section or shorter length, and decreases for longer, more slender shafts.
Last reviewed August 2026