Bolt Grade Converter
Look up equivalent bolt grades between metric (class) and SAE (grade) systems.
Find tensile strength for any bolt grade.
Select a bolt grade — see the equivalent in the other system.
Bolt Grade Details
Bolt grades indicate tensile strength (how much pulling force the bolt can handle).
SAE to Metric equivalents:
- SAE Grade 2 = Metric Class 4.6 (low strength, general purpose)
- SAE Grade 5 = Metric Class 8.8 (medium strength, most common)
- SAE Grade 8 = Metric Class 10.9 (high strength, heavy duty)
- No SAE equivalent = Metric Class 12.9 (very high strength, aerospace)
Tensile strength comparison:
- Grade 2 / Class 4.6: 60,000 psi (400 MPa)
- Grade 5 / Class 8.8: 120,000 psi (800 MPa)
- Grade 8 / Class 10.9: 150,000 psi (1,040 MPa)
- Class 12.9: 177,000 psi (1,220 MPa)
Identification marks:
- Grade 2: no marks on head
- Grade 5: 3 radial lines on head
- Grade 8: 6 radial lines on head
- Metric: class number stamped on head (e.g., “8.8”)