Click here - Printable Metric Bolt Grade Chart (PDF)Inch / Metric Ruler

Printable Chart for easy comparison between Metric Bolt Classes and US grades equivalents.

Head Markings

Metric Bolt Class

Mechanical Properties

Proof Load (MPa)

Min Yield (MPa)

Min Tensile Strength (MPa)

Metric Grade 12.9 strength chart

Class 12.9

Alloy Steel, quenched and tempered

970

1,100

1,220

Metric Grade 10.9 strength chart

Class 10.9

Alloy Steel, quenched and tempered

830

940

1,040

Metric Grade 8.8 strength chart

Class 8.8

Medium carbon steel, quenched and tempered

580-600

640-660

800-830

A4-80 Metric Strength Chart

A4-80 Stainless

Similar to 316, commonly used in Marine environments

N/A  600 800
A2-70 Metric Strength Chart

A2-70 Stainless

Most common stainless. Similar to 304 / 18-8

N/A

450

700

 

US/Imperial  

LBF/In²(PSI)  

  Metric 

  Mpa(N/mm²)

Chart for easy comparison of US / Metric screws and bolts.  It is always a bit unusual to compare them as they use different measurement systems (PSI vs. Mpa). 

 180,000  

 SAE Grade 8- 150,000  

SAE Grade 5 - 120,000  

  116,000  

101,530  

75,420  

SAE Grade 2 - 74,000  

58,020  

  1,220 - Class 12.9

  1,040 - Class 10.9

  830 - Class 8.8

  800 - Stainless A4-80

  700 - Stainless A2-70

  520 - Class 5.8

  510

  400 - Class 4.6

 

Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set.

Yield Strength: The maximum load at which a material exhibits a specific permanent deformation

1MPa = 1N/mm2 = 145 pounds/inch2

Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing.