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Bolt Shear & Tensile Strength Calculator

Check if your bolts can handle the load. Pick the bolt size, grade, and load. See tensile capacity, single shear, double shear, and safety factor instantly.

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Bolt Capacity
0 lbs
Tensile Capacity 0 lbs
Single Shear Capacity 0 lbs
Double Shear Capacity 0 lbs
Proof Load 0 lbs
Safety Factor --
Formulas used:
Tensile Capacity = Ftu × At
Single Shear = 0.60 × Ftu × At
Double Shear = 2 × Single Shear
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Uses Lame's thick-wall cylinder equations. Verify critical designs with FEA.

How Bolt Strength Works

A bolt has two ways to fail. It can break in tension when pulled. It can cut in shear when loaded sideways. This calculator checks both.

Bolt Grades

Bolt grade tells you the material strength. Grade 2 is soft. Grade 5 is medium. Grade 8 is strong. The head has marks to show the grade. Count the radial lines on the bolt head. Three lines means Grade 5. Six lines means Grade 8. No lines means Grade 2.

Metric Classes

Metric bolts use numbers like 8.8 and 10.9. The first number times 100 is the tensile strength in MPa. Class 8.8 has 800 MPa. The second number is the yield-to-tensile ratio. Higher numbers mean stronger bolts.

Shear vs Tensile

Tensile load pulls the bolt lengthwise. Think of hanging a weight from a bolt. Shear load pushes the bolt sideways. Think of two plates sliding past each other with a bolt holding them together. A bolt is stronger in tension than in shear.

Pro tip: When possible design joints in shear, not tension. Shear joints are more predictable and less sensitive to preload. Save tension for cases where shear is not possible.

Single vs Double Shear

Single shear has one cutting plane. Double shear has two. Double shear doubles the capacity because the load splits across two planes. A double-shear joint is the strongest way to use a bolt in shear.

Safety Factor

Safety factor is the bolt capacity divided by the applied load. A safety factor of 2.0 means the bolt can handle twice the load. Use 2.0 for static loads, 3.0 for cyclic, and 4.0 or more for critical or shock loads.

Frequently Asked Questions

Tensile strength is how much pulling force a bolt can take before breaking. It equals the ultimate stress of the bolt material times the tensile stress area of the threads. A Grade 8 half-inch bolt has about 17,000 pounds of tensile capacity.
Shear strength is how much sideways force a bolt can take before cutting. Single shear has one shear plane. Double shear has two shear planes and doubles the capacity. Shear strength is about 60 percent of tensile strength.
Grade 5 bolts have 120,000 psi tensile strength and three radial marks on the head. Grade 8 bolts have 150,000 psi and six radial marks. Grade 8 is stronger but also more brittle. Use Grade 8 for high-load joints and Grade 5 for general use.
Metric bolts use classes like 8.8, 10.9, and 12.9. Class 8.8 is similar to Grade 5. Class 10.9 is similar to Grade 8. Class 12.9 is the strongest common class at about 175,000 psi tensile.
Proof load is the maximum load a bolt can take without permanent stretching. It is about 90 percent of yield strength. Staying below proof load means the bolt can be reused.
Use a safety factor of 2.0 for static loads and 3 to 5 for cyclic or shock loads. Aerospace and medical use 4.0 or higher. This calculator shows a green, yellow, or red safety check based on your load.
No, this calculator covers bolt breakage only. For thread stripping check our Thread Engagement Length Calculator. Thread stripping happens when the tapped hole material is weaker than the bolt.
Single shear means the bolt is cut along one plane, like a bolt through two plates. Double shear means the bolt is cut along two planes, like a bolt through three plates. Double shear doubles the shear capacity.
Tensile stress area is the effective cross-section area that carries the load through the threads. It is smaller than the major diameter area because the threads reduce the material. The calculator uses the correct area for each bolt size.
Yes. A2/A4 stainless has about 70,000 psi tensile strength, similar to Grade 2 mild steel. A2-70 or A4-80 grades are stronger. For high-load joints in corrosive environments, use Grade 8 with a coating instead.

Bolt Grade Strength Reference

Grade / Class Tensile Strength Yield Strength Common Use
Grade 2 (SAE)60,000 psi36,000 psiGeneral purpose, non-critical
Grade 5 (SAE)120,000 psi92,000 psiAutomotive, structural
Grade 8 (SAE)150,000 psi130,000 psiHigh-strength, heavy equipment
A2/A4 Stainless75,000 psi30,000 psiCorrosion-resistant, food grade
Class 8.8 (metric)116,000 psi93,000 psiStandard metric automotive
Class 10.9 (metric)151,000 psi136,000 psiHigh-strength metric
Class 12.9 (metric)177,000 psi160,000 psiAerospace, critical joints

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