Engineering · Calculators

Bolt torque calculator.

Nominal torque scenario for inch and metric bolts using T = KDF. Not an assembly specification: joint design and measured friction determine the approved preload and torque.

Torque — ft-lb · — N·m details ↓

Bolt size Bolt grade / strength

Preload as % of yield %

The default is an illustrative 75% of nominal yield preload, not a universal assembly specification. Select preload from the joint design, including torque scatter, proof load, fatigue, bearing and thread-stripping checks.

Nominal torque

Imperial

— ft-lb

— in-lb

Metric

— N·m

Tensile area:—

Yield strength:—

Preload force:—

Nut factor (K):—

Send these numbers to a quote →

For aerospace/critical joints, cross-check with the OEM specification. For tapped holes in soft material (aluminum, plastics), reduce torque to limit thread engagement strain.

Nominal Preload / Yield Ratio

75%

of yield strength

Torque Energy Distribution

11%

49%

40%

Preload (11%) Under-head (49%) Thread (40%)

Illustrative friction split only: the nut factor K does not uniquely determine head/thread friction allocation. Actual preload scatter depends on the fastener, joint, lubrication and tightening method; this display is not a joint-safety check.

Joint Simulator

Fastener Preload & Plate Compression

Joint analysis required

Elongation / Stretch

0.0000″ elastic stretch

Elastic Stress

0.0 ksi of 92.0 ksi yield

Calculation method: T = K × D × F, where T is torque, K is the nut factor (varies by lubrication, default 0.20 dry steel), D is nominal bolt diameter, and F is the target preload force (75% × yield × tensile stress area).

Keep exploring

Related tools & references

Thread engagement calculator→

Engagement length so the joint fails the bolt, not the threads.

Thread specs reference→

Tensile stress areas and pitch behind these torque values.

Tap drill calculator→

Pick the right tap drill for the mating tapped hole.

Clearance hole chart→

Through-hole sizes for bolted joints.

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