Calculated Result
Enter your data and press calculate. The computed torque will appear here above the form.
Calculator Inputs
Torque Trend Chart
The graph updates after calculation and shows how torque changes with the key driving variable for the selected method.
Formula Used
Metric: T = 9550 × P / N, where torque is in N·m, power in kW, and speed in rpm.
Imperial: T = 5252 × HP / rpm, where torque is in lb-ft.
T = F × r, where F is tangential force and r is lever arm radius.
T = (π/16) × τ × d³, where τ is allowable shear stress and d is shaft diameter.
T = (π/16) × τ × ((D⁴ − d⁴) / D), where D is outer diameter and d is inner diameter.
Allowable torque shown above equals calculated torque divided by the selected safety factor.
How to Use This Calculator
Choose the formula that matches your engineering case, such as motor power transmission or shaft torsion capacity.
Pick metric or imperial mode first so every input and result follows the correct convention.
Fill in the visible fields only. Hidden fields belong to other methods and are not used.
Use a realistic safety factor to convert theoretical capacity into a more conservative allowable torque.
The result block above the form displays maximum torque, allowable torque, and the selected method summary.
Use the CSV and PDF buttons to save your result for reports, handoff notes, or design checks.
Example Data Table
| Scenario | Input Set | Method | Estimated Torque |
|---|---|---|---|
| Motor drive | 15 kW, 1450 rpm, 95% efficiency | Power and Speed | 93.85 N·m |
| Lever arm | 420 N, 0.32 m radius | Force and Radius | 134.40 N·m |
| Solid shaft | 60 MPa, 32 mm diameter | Solid Shaft Torsion | 385918.49 N·mm |
| Hollow shaft | 55 MPa, 60 mm OD, 30 mm ID | Hollow Shaft Torsion | 1968593.74 N·mm |
Frequently Asked Questions
1. What is maximum torque?
Maximum torque is the highest twisting moment a system can transmit or resist before limits such as stress, yielding, or design constraints are reached.
2. Which method should I choose?
Use power and speed for motors, force and radius for levers or pulleys, and torsion formulas for shaft strength checks.
3. Why is allowable torque lower than maximum torque?
Allowable torque applies the safety factor. It gives a more conservative design value than the raw theoretical or calculated maximum torque.
4. Does efficiency affect torque?
Yes. In power transmission calculations, lower efficiency means less useful transmitted torque reaches the output shaft.
5. Why does shaft diameter matter so much?
Torque capacity increases rapidly with diameter because torsional capacity depends on the cube of diameter for solid shafts.
6. Can I use this for hollow shafts?
Yes. The hollow shaft mode accounts for both outer and inner diameters, which significantly changes torsional capacity.
7. Are the results suitable for final design approval?
This tool is useful for engineering estimates and checks, but final approval should include materials, fatigue, temperature, and code requirements.
8. What units are returned?
Metric calculations return N·m or N·mm depending on the method. Imperial calculations return lb-ft or lb-in.