Mr Calcu | Get precise bolt torque values in seconds—engineered for speed, accuracy, and peace of mind.

Free bolt torque calculator for engineers and mechanics. Get precise Nm/lb-ft values for steel, aluminum, and lubricated fasteners instantly.

Bolt Torque Calculator

Bolt Torque Calculator Guidelines

Confident tightening starts with the right numbers.

Usage Guidelines

Input: Select bolt diameter, material, and surface condition (dry/lubricated/zinc-coated)
Output: Torque values in Nm and lb-ft for common preload scenarios

Common Scenarios

Automotive lug nuts: 85–150 lb-ft
Structural bolts (AISC): M20–M30, torqued to 400–1000 Nm
Engine assemblies: Torque-to-yield bolts, use with angle gauges

Edge Cases

Titanium fasteners: Reduce torque by 25%, use anti-seize to prevent galling
Galvanized bolts: Apply torque reduction (30–40%) due to low friction
Thread-locking adhesives: Increase torque by 10% to overcome chemical resistance
Double-nutted bolts: Account for extra friction—torque the first nut, then the jam nut
Long bolts: Use tension-based methods (elongation or ultrasonic) to avoid twist-related errors

Bolt Torque Calculator Description

What Is Bolt Torque?

Bolt torque is the rotational force applied to a threaded fastener to generate a specific preload or clamping force. Proper torque ensures mechanical reliability and prevents vibration-induced loosening or failure.

Why It Matters

Ensures structural integrity under load
Minimizes thread failure and fatigue
Complies with engineering codes and standards

According to ASTM and SAE, bolt torque must account for material yield strength, thread geometry, and friction factors.

Torque Formula & Derivation

Use the following equation to calculate torque based on material and conditions:

T = K × D × F

T: Torque (Nm or lb-ft)
K: Nut factor (0.2 dry, 0.16 lubricated, 0.12 zinc-coated)
D: Bolt diameter (m or in)
F: Clamp force (N or lbf)

Engineering Insight

This formula provides a simplified model. For critical joints, consider advanced methods that include:

Thread pitch angle corrections
Underhead friction variation
Material elastic deformation

Pro Tip: When working with large bolts or structural steel, use the turn-of-nut method for more accurate preload than torque alone.

Case Study Examples

Aerospace Engine Bracket

Material: Titanium bolts
Required torque: 220 Nm
Issue: Galling and preload loss
Solution: Apply anti-seize and reduce torque by 25%

Steel Beam Connection

Material: Galvanized M24 bolts
Standard torque: 720 Nm
Adjusted for zinc coating: 430 Nm
Reason: Lower friction coefficient (~0.12)

Start calculating now and eliminate the guesswork—your fasteners deserve precision.

Example Calculation

Bolt Size (mm)	Material	Dry (Nm)	Lubricated (Nm)	Zinc Coated (Nm)
M6	Steel	10	8.5	6.8
M10	Steel	47	40	32
M16	Steel	160	136	108
M12	Aluminum	55	44	38
M24	Galvanized Steel	720	—	430
M10	Titanium	50	42	—

Frequently Asked Questions

Dry steel M12 bolts typically require 80 Nm; lubricated bolts need ~68 Nm; zinc-coated versions require ~55 Nm.

Lubrication reduces thread and under-head friction, decreasing required torque by 15–25% for the same preload.

Yes. Most cars require 85–150 lb-ft; always confirm with vehicle manufacturer specs for accurate torque.

The nut factor is an empirical coefficient accounting for friction. It varies by material, surface finish, and lubrication: 0.2 (dry steel), 0.16 (lubricated), 0.12 (zinc-coated).

Titanium has a lower modulus of elasticity and is prone to galling. Using anti-seize and reducing torque by 20–25% helps prevent thread damage.

No. Torque is only an indirect measure of preload and is affected by friction. Use direct tension measurement (e.g., strain gauges or elongation) in critical applications.

Multiply the torque value in Newton-meters (Nm) by 0.73756 to get pound-feet (lb-ft). For example, 100 Nm × 0.73756 = 73.76 lb-ft.

Mr Calcu | Get precise bolt torque values in seconds—engineered for speed, accuracy, and peace of mind.

Bolt Torque Calculator

Bolt Torque Calculator Guidelines

Usage Guidelines

Common Scenarios

Edge Cases

Bolt Torque Calculator Description

What Is Bolt Torque?

Why It Matters

Torque Formula & Derivation

Engineering Insight

Case Study Examples

Aerospace Engine Bracket

Steel Beam Connection

Example Calculation

Frequently Asked Questions

What’s the torque for an M12 bolt?

How does lubrication affect torque?

Can I use this for wheel lug nuts?

What is the nut factor (K), and how is it determined?

Why do titanium bolts need less torque?

Can torque alone guarantee bolt preload?

How do I convert Nm to lb-ft for torque specs?

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