🔧 Rotational Stiffness Calculator
Calculate the rotational (torsional) stiffness of a shaft or spring from applied torque and the resulting angle of twist.
What rotational stiffness is
Rotational (torsional) stiffness describes how much a shaft, spring, or structural element resists twisting under an applied torque — higher stiffness means less angular deflection for the same torque.
The formula
Rotational stiffness k = T / θ, where T is the applied torque and θ is the resulting angle of twist, expressed in radians (k is typically given in N·m per radian). This is analogous to linear stiffness (spring constant), but for rotational rather than linear displacement.
This calculator finds stiffness from measured torque and twist; for design purposes, torsional stiffness can also be derived from shaft geometry and material shear modulus (k = GJ/L).