A Bolt Tensile Strength Chart is very important for engineers and purchasers to determine the tensile strength of each bolt grade available from Grade 4.8 to Grade 12.9, including various grades of Stainless Steel. This will assist you in picking the correct type of bolt for specific application requirements based on load, safety factor, and condition of use. The comprehension of tensile strength will assure better performance and cost-efficiency in your applications. At Jade Alloys, we provide precision-engineered bolts across all major grades with consistent quality and global supply support, helping industries choose the right fastener for critical applications.
Why Tensile Strength Matters in Bolt Selection
A bolted joint operates on the principle of clamping force that is generated when a bolt is tightened and slightly stressed. These are three properties that control it: tensile strength (maximum load before breaking), yield strength (point at which permanent deformation begins) and proof load (safe load without permanent stretch). In practice, bolts are tightened below the proof load, to keep them within the elastic range. The wrong grade can result in a loss of clamp force and/or environmental damage such as corrosion or embrittlement. That’s why it becomes very important to check the grade tensile strength before using it in any structure.
Metric Bolt Grade Tensile Strength Chart (ISO 898-1)
The following table covers all standard metric property classes defined in ISO 898-1:2022 for bolts, screws, and studs in carbon and alloy steel. Grades are arranged in ascending strength order. For a detailed breakdown of the highest grade, see the grade 12.9 bolt specifications guide.
| Grade | Min Tensile StrengthRm (MPa) | Min Yield StrengthRp0.2 (MPa) | Proof Load StressSp (MPa) | Hardness | Typical Material & Heat Treatment |
| 4.6 | 400 | 240 | 225 | 120–220 HV | Low or medium carbon steel, no heat treatment |
| 4.8 | 420 | 340 | 310 | 130–220 HV | Low or medium carbon steel, partially cold-worked |
| 5.8 | 520 | 420 | 380 | 155–220 HV | Low or medium carbon steel, cold-worked |
| 6.8 | 600 | 480 | 440 | 181–250 HV | Medium carbon steel, cold-worked |
| 8.8 | 800 | 640 | 580 | 22–32 HRC | Medium carbon steel or alloy steel, quenched & tempered (ge M16) |
| 10.9 | 1,040 | 940 | 830 | 32–39 HRC | Alloy steel (Cr, Cr-Mo), quenched & tempered |
| 12.9 | 1,220 | 1,100 | 1,100 | 39–44 HRC | Alloy steel (Cr-Mo, Cr-Ni-Mo), quenched & tempered |
Stainless Steel Bolt Strength Chart (ISO 3506)
The Stainless steel bolts are made in accordance with ISO 3506-1, which is also known sometimes represented as a stainless steel type, represented as steel type (A = austenitic), the number is the group, and the suffix represents tensile strength (units of 10 MPa). A4-70, for instance, represents SS 316 and 700MPa Tensile Strength.
Stainless steel bolts are very corrosion resistant but are not as strong as alloy steel bolts. The highest grades are A2-80/A4-80, which are around 800 MPa, close to Grade 8.8. The 12.9 strength is not obtainable in stainless steel as it does not get that hard in the heat treatable process.
| Grade | Steel Type | UNS / EN Equiv. | Min Tensile Rm (MPa) | Min Yield Rp0.2 (MPa) | Max Hardness (HV) | ISO 898-1 Approx. Equiv. |
| A2-50 | SS 304 | S30400 / 1.4301 | 500 | 210 | 210 | Below 4.6 |
| A2-70 | SS 304 | S30400 / 1.4301 | 700 | 450 | 250 | ~6.8 / 8.8 |
| A2-80 | SS 304 | S30400 / 1.4301 | 800 | 640 | 250 | ≈ 8.8 |
| A4-50 | SS 316 | S31600 / 1.4401 | 500 | 210 | 210 | Below 4.6 |
| A4-70 | SS 316 | S31600 / 1.4401 | 700 | 450 | 250 | ~6.8 / 8.8 |
| A4-80 | SS 316 | S31600 / 1.4401 | 800 | 640 | 250 | ≈ 8.8 |
High-Temperature Bolt Grades (ASTM A193)
Carbon steel grades (ISO 898-1) and stainless grades (ISO 3506) are generally not code allowed for bolting in pressure vessels, flanged piping, and valve bodies when operating at temperatures above 300 °C. ASTM A193 is the governing specification for high temperature/high pressure bolting. See the ASTM A193 overview for a complete guide.
| Grade | Material & Heat Treatment | Min TensileRm (MPa) | Min YieldRp0.2 (MPa) | Max ServiceTemp (°C) | Primary Application |
| B7 | Cr-Mo alloy steel (4140/4142),Quenched & Tempered | 1,035 | 862 | ~450°C | Carbon steel flanges, pressure vessels, standard high-temperature service. |
| B16 | Cr-Mo-V alloy steel,Quenched & Tempered | 1,035 | 862 | ~510°C | Elevated-temperature service above the B7 range; highly utilized in power generation. |
| B8 Class 2 | SS 304,Strain-hardened (Cold-worked) | 860 | 690 | ~540°C (derated above 300°C) | Stainless steel flanges, food processing plants, general corrosion-resistant service. |
| B8M Class 2 | SS 316,Strain-hardened (Cold-worked) | 860 | 690 | ~540°C (derated above 300°C) | Marine, offshore, chloride environments; elevated-temperature stainless service. |
How to Read Bolt Grade Markings
The classification and designation of bolt grades as described in ISO 898-1 provide engineers with a quick way to establish the strength of the bolt by just looking at its head markings. The number signifies its tensile strength and the yield ratio; for example, 8.8, 10.9, and 12.9 denote different levels of strength in the bolt, according to this system. Other grades, such as the stainless grade, A4-70, follow a slightly different method whereby the letters denote the steel grade (austenitic) while the number identifies the category (SS 316) and the tensile strength, respectively. All bolt types should bear a manufacturer’s marking.
Tensile Load Capacity by Bolt Size and Grade
| Size | Pitch (mm)Coarse | Tensile Stress Area (mm2) | Grade 4.8 | Grade 8.8 | Grade 10.9 | Grade 12.9 |
| M10 | 1.50 | 58.0 | 24.4 | 46.4 | 60.3 | 70.8 |
| M12 | 1.75 | 84.3 | 35.4 | 67.4 | 87.7 | 102.8 |
| M14 | 2.00 | 115.0 | 48.3 | 92.0 | 119.6 | 140.3 |
| M16 | 2.00 | 157.0 | 65.9 | 125.6 | 163.3 | 191.5 |
| M18 | 2.50 | 192.0 | 80.6 | 153.6 | 199.7 | 234.2 |
| M20 | 2.50 | 245.0 | 102.9 | 196.0 | 254.8 | 298.9 |
| M22 | 2.50 | 303.0 | 127.3 | 242.4 | 315.1 | 369.7 |
| M24 | 3.00 | 353.0 | 148.3 | 282.4 | 367.1 | 430.7 |
| M27 | 3.00 | 459.0 | 192.8 | 367.2 | 477.4 | 559.9 |
| M30 | 3.50 | 561.0 | 235.6 | 448.8 | 583.4 | 684.4 |
| M33 | 3.50 | 694.0 | 291.5 | 555.2 | 721.8 | 846.7 |
| M36 | 4.00 | 817.0 | 343.1 | 653.6 | 849.7 | 996.7 |
How to Choose the Right Bolt Grade for Your Application
Choosing the right bolt grade is crucial for ensuring joint safety, performance, and reliability. Apply this easy 3-step strategy:
Calculate Joint Load
Calculate the total load on the joint, involving static, dynamic and shock loads. This is the minimum strength requirement of the bolt.
Check the Environment
Assess exposures including moisture, chemicals, temperature, and/or corrosion. In corrosive environment, use stainless steel or coated bolts; in high strength dry environment, use alloy steel.
Match Grade to Proof Load (with Safety Margin)
Choose a bolt that has a proof load that is 25% greater than the working load. This keeps the bolt in the elastic range and keeps its clamping force constant with time.
This provides an iterative approach to help engineers prevent under-specification (potential failure) and over-specification (excessive cost).
Explore our range of hex bolts built for strong and reliable fastening in structural applications. For high-load performance, our alloy steel bolts deliver superior strength and durability. If corrosion resistance is critical, choose our stainless steel bolts designed for harsh environments. We also supply ASTM A193 B7 bolts, ideal for high-pressure and high-temperature industrial use.
Need High-Tensile Bolts with Full Mill Certification?
Jade Alloys supplies grade 8.8, 10.9, 12.9 metric bolts and ASTM A193 B7 studs with complete mill test certificates covering chemical composition, mechanical properties, and hardness. Standard and custom sizes available ex-India.
