This page provides tensile strength and proof stress data for metric bolts and screws in accordance with ISO 898-1. The tables include common property classes (3.6 to 12.9) and allow quick reference for engineering design and material selection.
Metric bolt property classes (e.g. 8.8, 10.9) define the material strength and yield characteristics of the fastener.
Indicated stresses in Newton/mm2
Indicated stresses in Newton/mm²
| Strength Designation | 3.6 | 4.6 | 4.8 | 5.6 | 5.8 | 6.8 | 8.8 =< 16mm |
8.8 > 16 |
9.8 | 10.9 | 12.9 |
| Nom. Tensile Strength | 300 | 400 | 400 | 500 | 500 | 600 | 800 | 800 | 900 | 1000 | 1200 | Min Tensile Strength | 330 | 400 | 420 | 500 | 520 | 600 | 800 | 830 | 900 | 1000 | 1200 |
| Lower Yield Stress | 180/190 | 240 | 320/340 | 300 | 400/420 | 480 | - | - | - | - | - |
| Stress at Perm. Set | - | - | - | - | - | - | 640 | 640/660 | 720 | 900/940 | 1080/100 |
In accordance with BS 3692:2001 and BS EN IOS 898-1 : 1999
Indicated stresses in Newton/mm2
| Strength Designation | 4 | 5 | 6 | 8 | 10 | 12 |
| Tensile Strength | 400 | 500 | 600 | 800 | 1000 | 1200 |
In accordance with BS 3692:2001
The designation system allows the determination of the ultimate and yield/proof strength of
the bolt. The designation system is based on two numbers e.g 8.8 . The first number is
the tensile strength of the bolt material (N2 )/100. The second number is
= 1/100.(the ratio of the Proof (or Yield ) stress and the Tensile strength expressed
as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100
The tensile and proof strength of the steel for a 4.6 bolt is therefore calculated
as follows
Tensile strength (Rm) = 4.100 N/mm2 = 400 N/mm2 .... Proof strength (R0,2) = 0,6*400 * 100 /100 = 240 N/mm2
Stainless steels include Austenitic, Martensitic and Ferritic..
Austenitic stainless steels..
Chromium nickel steels which can be cold worked. Non magnetic.
Associated grades ( Steel Number according to BS EN 10088 pt 1) = A1 (1.4305) ,
A2 (1.4301) ,A3 (1.4541) , A4 (1.4401) and A5 (1.4571).
Martensitic stainless steels ..
Limited corrosion resistance but can be heat treated for superior strength properties. Magnetic Properties.
Associated grades ( Steel Number according to BS EN 10088 pt 1) = C1 (1.4006 etc) , C3 (1.4057), C4(1.4104)
Ferritic stainless steels ..
Plain chromium stainless steels with a chromium content varying between 10.5
and 18% and a low carbon content. They not hardenable by heat treatment.
Ferritic alloys have good ductility and formability but a relatively poor high
temperature strength compared austenitic grades. Magnetic..
Associated grades = F1
Indicated stresses in Newton/mm2
| Stainless Steel | Austenitic | Martensitic | Ferritic | |||||||
| Steel Grade | A1, A2, A3, A4, A5 | C1,C4 | C1 | C3 | F1 | |||||
| Strength class | 50 | 70 | 80 | 100 | 50 | 70 | 110 | 80 | 45 | 60 |
| Tensile Strength | 500 | 700 | 800 | 1000 | 500 | 700 | 1100 | 800 | 450 | 600 |
| 0,2% proof stress | 210 | 450 | 600 | 750 | 250 | 410 | 820 | 640 | 250 | 410 |
Use these calculators to apply bolt strength, proof load and tensile stress data to practical fastener checks.
| Calculator | Use |
| Bolted Joint and Fastener Calculators | Main hub for RoyMech bolt stress, preload, thread and layout calculators. |
| Bolt Tensile Stress Calculator | Calculate tensile stress from axial bolt load and bolt diameter. |
| Thread Tensile Stress Area Calculator | Calculate ISO metric thread tensile stress area from diameter and pitch. |
| Bolt Proof Load Calculator | Calculate proof load from proof stress and tensile stress area. |
| Bolt Shear Stress Calculator | Calculate single shear and double shear stress in a bolt. |
| Bolt Combined Stress Calculator | Check combined tensile and shear stress in a bolt. |