Shaft Diameter Calculator
Enter torque, bending moment, and material yield strength to get the minimum required shaft diameter using ASME design criteria.
Shaft Loads & Material
Steel 1045: ~450 MPa • Mild steel: ~250 MPa • 4340: ~470 MPa
SCF = stress concentration factor. Use 1.0 for smooth shafts; higher for keyways or fillets.
Enter loads and click Calculate to see the minimum shaft diameter.
Minimum Shaft Diameter
—
mm
(— in)
Equivalent Bending Moment
— N·m
Allowable Stress
— MPa
Formula Used
Round up the result to the nearest standard shaft size for procurement.
Summary
Enter torque, bending moment, and material yield strength to get the minimum required shaft diameter using ASME design criteria.
How it works
- Enter the applied bending moment (M) and torsional moment (T) in N·m.
- Provide the material yield strength (Sy) in MPa.
- Set the desired safety factor (typically 1.5–3 for rotating shafts).
- Optionally enter fatigue stress concentration factors for bending (Kb) and torsion (Kt).
- Select the design criterion: ASME von Mises or Maximum Shear Stress (Tresca).
- Click Calculate to see the minimum shaft diameter in mm and inches.
Use cases
- Sizing motor output shafts and drive shafts in machinery.
- Checking existing shaft designs against ASME standards.
- Preliminary shaft sizing during mechanical system design.
- Educational demonstration of combined-load shaft design equations.
- Comparing von Mises vs. Tresca failure criteria on a real design.
- Accounting for stress concentration factors at keyways and fillets.
- Converting shaft dimensions between metric and imperial units.
- Rapid design iterations when exploring different materials.
Frequently Asked Questions
Last updated: 2026-06-11 ·
Reviewed by Nham Vu