Calculate torque from preload, diameter, and factors. Switch units, export results, and inspect example values. Improve assembly consistency with clear steps and formula notes.
| Case | System | Diameter | Pitch or TPI | Nut Factor | Preload Method | Total Torque | Handle Force |
|---|---|---|---|---|---|---|---|
| Metric M12 | Metric | 12 mm | 1.75 mm | 0.20 | Estimated from 830 MPa at 75% | 140.48 N·m | 561.93 N at 250 mm |
| Imperial 1/2-13 | Imperial | 0.50 in | 13 TPI | 0.20 | Estimated from 85000 psi at 75% | 1010.07 lbf·in | 101.01 lbf at 10 in |
| Metric M16 | Metric | 16 mm | 2.00 mm | 0.18 | Estimated from 830 MPa at 70% | 286.12 N·m | 953.74 N at 300 mm |
Base torque: T = K × F × d
T is tightening torque.
K is the nut factor.
F is preload or clamp load.
d is nominal bolt diameter.
Total torque: Total Torque = (Base Torque × (1 + Allowance)) + Prevailing Torque
Metric stress area estimate: A = π/4 × (d − 0.9382p)²
Imperial stress area estimate: A = 0.7854 × (d − 0.9743/n)²
Estimated preload: F = A × Proof Strength × Target Load %
Handle force: Wrench Force = Torque / Lever Arm
These equations give a practical field estimate. Real torque scatter changes with lubrication, coating, thread finish, washer use, seating condition, and tool calibration.
Step 1: Choose metric or imperial input mode.
Step 2: Enter nominal diameter and thread pitch or TPI.
Step 3: Add a direct preload value if you already know it.
Step 4: If preload is unknown, enter proof strength and target proof load.
Step 5: Enter nut factor, prevailing torque, and tightening allowance.
Step 6: Enter wrench length and fastener quantity.
Step 7: Press the calculate button.
Step 8: Review torque, preload, handle force, and combined clamp load.
Step 9: Export the result to CSV or PDF for job records.
A nut torque calculator helps estimate tightening torque for threaded joints. It converts preload targets into practical torque values. This matters in assembly, maintenance, fabrication, and field repair. Good torque control supports clamp load, joint stability, and repeatable performance.
Preload is the tension created in a fastener during tightening. That tension clamps joint members together. Too little preload can allow loosening, leakage, or movement. Too much preload can damage threads, deform parts, or push a fastener beyond proof load. Torque is only an indirect path to preload, so field estimates must be handled with care.
Nut factor is one of the biggest drivers. It represents friction effects in threads and under the nut face. Lubrication, coating, surface finish, and washer condition can change it quickly. Diameter also changes torque because larger fasteners create more moment arm. Prevailing torque raises the required turning effort. Wrench length affects the hand force needed during installation.
When direct preload is unknown, this page can estimate it from tensile stress area, proof strength, and target proof load percentage. That approach is useful for planning. It gives a sound engineering starting point for bolt tightening procedures, work instructions, and inspection sheets. It does not replace validated torque-tension testing for critical joints.
This nut torque calculator suits machinery assembly, equipment maintenance, structural connections, piping supports, brackets, and workshop fixtures. It is also useful when comparing metric and imperial values across mixed projects. The export options help create simple job records, training examples, and review notes for technicians and engineers.
Use clean threads, known lubrication, and calibrated tools. Recheck assumptions before production use. For safety critical or fatigue sensitive joints, confirm torque with approved standards, tool data, and physical verification methods such as bolt elongation, load indication, or torque-angle validation.
Nut factor is a simplified friction factor. It links preload, diameter, and torque. A small change in friction can change torque a lot, so use realistic values for dry or lubricated conditions.
Proof strength helps estimate allowable preload when direct clamp load is unknown. It gives a planning value based on fastener capacity and target loading percentage.
Use direct preload when measured or specified data exists. Use estimated preload when you are planning, comparing options, or building an initial tightening procedure.
No. Torque is the turning effort applied during tightening. Preload is the tension created inside the fastener. Torque only estimates preload because friction consumes much of the input energy.
Prevailing torque is extra torque needed to turn a locking nut or resist thread friction before clamp load is fully developed. It should be added to the tightening calculation.
Yes. The calculator supports both systems. It also shows converted torque outputs so you can compare workshop values, wrench settings, and documentation units more easily.
Handle force shows how much effort reaches the wrench handle. It helps technicians judge tool choice, lever length, and whether a manual tightening approach is practical.
It is a strong planning tool, but critical joints need validated procedures. Use project standards, material data, tool calibration, and physical verification methods before final release.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.