Drawing No. EH–ME–012 // Mechanical Engineering
Quick Shaft Sizing Calculator
Reviewed August 2026
A fast torsion-dominated shaft sizing tool for preliminary solid or hollow shaft diameter selection from power and RPM.
Calculation workflow
Inputs are converted internally to SI, the engineering model is solved, and results are converted back to the selected unit system.
Quick sizing inputs
Results
Background
Useful for first-pass transmission-shaft sizing when torque is the dominant load.
τ = 16T / [πD³(1-k⁴)]
For a solid shaft k = 0. The calculator multiplies operating torque by the entered torsional service factor before sizing.
Frequently asked questions
Practical questions about assumptions, limits and interpretation.
The quick calculator uses torsion only: maximum torsional shear stress in a circular solid or hollow shaft is limited to the entered allowable shear stress.
Use the full design tool whenever bending moment is significant, or when you need a combined-stress safety factor and angle-of-twist check.
Use an allowable value appropriate to the shaft material, safety factor, fatigue duty, stress concentrations and governing design method. This tool deliberately does not invent an allowable stress.
No. The entered torsional factor is only a load multiplier. Keyways and shoulders introduce local stress concentrations that require separate assessment.