US Bolt Grades & Strength Chart — SAE Grades 1–8.2 and ASTM A307/A449/A325/A354/A490, Minimum Strengths
Minimum strength values for US inch-series bolts — SAE Grades 1, 2, 4, 5, 5.2, 7, 8, 8.2 and ASTM A307, A449, A325 (Types 1/2/3), A354 (BC/BD), A490 (Types 1/3) — proof, tensile and yield minimums in ksi per size range, transcribed row-for-row from the collected strength chart.
Last updated: 2026-11
Specifications
Inch-series bolt strength is not one number per bolt — it is a grade-and-size-range pair, and the boundaries matter. The collected chart lays out the US ladder: SAE Grade 2 runs 55 ksi proof / 74 tensile / 57 yield up to 3/4 in, then drops to the Grade 1 set (33/60/36) from 7/8 in — the single most expensive mistake in grade selection, buying a "Grade 2" large bolt that is really a Grade 1 in strength. Grade 5 carries 85/120/92 through 1 in and falls to 74/105/81 (the A449 row) from 1 1/8 in; A325 structural bolts mirror Grade 5 across Types 1, 2 and 3 (weathering steel); Grade 8 and A354 BD hold 120/150/130 across the full 1/4–1 1/2 in range; A354 BC splits 105/125/109 small and 95/115 large with the yield column unprinted on its upper range (flagged). The source notes minimums are those exceeded by 99 percent of fasteners — a statistical floor, not a per-bolt guarantee — and its merged-cell layout groups markings over shared grades (A307 over Grade 1, A449 over the Grade 5 upper ranges). Material callouts reproduce as printed, including the A354 BC row the chart labels "weathering steel, quench and temper" — flagged, since BC is normally alloy steel; verify against the ASTM document before relying on it. Size ranges print in the source's mixed fraction style ("3/2" = 1 1/2 in). What the chart is not: a metric conversion (Grades 5/8 are not property classes 8.8/10.9, the geometry and proof-load definitions differ), a torque table, or a hardness spec — those are RFQ or standards-document items.
| Coverage | 23 grade/size-range rows: SAE Grades 1, 2, 4, 5, 5.2, 7, 8, 8.2; ASTM A307, A449, A325 Types 1/2/3, A354 BC/BD, A490 Types 1/3 — inch series, 1/4 to 4 in by row |
|---|---|
| Minimum strengths (ksi) | Proof / tensile / yield per grade and size range — Grade 2: 55/74/57 to 3/4 in, 33/60/36 from 7/8 in; Grade 5: 85/120/92 to 1 in, 74/105/81 from 1 1/8 in; Grade 8 & A354 BD: 120/150/130; A354 BC: 105/125/109 (1/4–2 1/2 in), 95/115 (2 3/4–4 in, yield not printed) |
| Statistical basis | Source note: minimum strengths are exceeded by 99 percent of fasteners — a reliability floor for the population, not a per-piece guarantee |
| Materials as printed | Low/medium carbon (Grades 1, 2, A307); medium carbon Q&T (Grades 5, 7, A325 Type 1, A449); low-carbon martensite Q&T (5.2, A325 Type 2); weathering steel Q&T (A325 Type 3, A490 Type 3, and A354 BC as printed — flagged); alloy steel Q&T (Grade 8, A354 BD, A490 Type 1) |
| Not in this chart | Proof-load values, hardness ranges, torque specs, metric property-class equivalents and fatigue data are not tabulated — per RFQ (state grade, size range and required certificates) |
| Bolt Grade Marking | Bolt Grade | Bolt Material | Bolt Size Range (in) | Min. Proof Strength (10^3 psi) | Min. Tensile Strength (10^3 psi) | Min. Yield Strength (10^3 psi) |
|---|---|---|---|---|---|---|
| SAE Grade 1 | Low or medium carbon | 1/4 to 3/2 | 33 | 60 | 36 | |
| ASTM A307 | Low carbon | 1/4 to 3/2 | 33 | 60 | 36 | |
| SAE Grade 2 | Low or medium carbon | 1/4 to 3/4 | 55 | 74 | 57 | |
| 7/8 to 3/2 | 33 | 60 | 36 | |||
| SAE Grade 4 | Medium carbon, cold drawn | 1/4 to 3/2 | 65 | 115 | 100 | |
| SAE Grade 5 | Medium carbon, quench and temper | 1/4 to 1 | 85 | 120 | 92 | |
| ASTM A449 | 9/8 to 3/2 | 74 | 105 | 81 | ||
| ASTM A449 | 7/4 to 3 | 55 | 90 | 58 | ||
| SAE Grade 5.2 | Low-carbon martensite, quench and temper | 1/4 to 1 | 85 | 120 | 92 | |
| ASTM A325, Type 1 | Medium carbon, quench and temper | 1/2 to 1 | 85 | 120 | 92 | |
| 9/8 to 3/2 | 74 | 105 | 81 | |||
| ASTM A325, Type 2 | Low-carbon martensite, quench and temper | 1/2 to 1 | 85 | 120 | 92 | |
| 9/8 to 3/2 | 74 | 105 | 81 | |||
| ASTM A325, Type 3 | Weathering steel, quench and temper | 1/2 to 1 | 85 | 120 | 92 | |
| 9/8 to 3/2 | 74 | 105 | 81 | |||
| ASTM A354, Grade BC | Weathering steel, quench and temper | 1/4 to 5/2 | 105 | 125 | 109 | |
| 11/4 to 4 | 95 | 115 | ||||
| SAE Grade 7 | Medium-carbon alloy, quench and temper | 1/4 to 3/2 | 105 | 133 | 115 | |
| SAE Grade 8 | Medium-carbon alloy, quench and temper | 1/4 to 3/2 | 120 | 150 | 130 | |
| ASTM A354, Grade BD | Alloy steel, quench and temper | 1/4 to 3/2 | 120 | 150 | 130 | |
| SAE Grade 8.2 | Low-carbon martensite, quench and temper | 1/4 to 1 | 120 | 150 | 130 | |
| ASTM A490, Type 1 | Alloy steel, quench and temper | 1/2 to 3/2 | 120 | 150 | 130 | |
| ASTM A490, Type 3 | Weathering steel, quench and temper |
- Row 2 (ASTM A307): The source merges the marking and grade cells for ASTM A307 (printed once in the flattened first column); reproduced as a single marking entry with the grade cell left empty.
- Row 4 (): Continuation size-range row (7/8 to 3/2) for the grade above — the source table's merged cells print no marking/grade/material on this line; values belong to the preceding grade row's second size range.
- Row 7 (ASTM A449): Marking "ASTM A449" printed alone in the flattened first column for the 9/8 to 3/2 size range — the source's merged cells carry no separate grade/material on this line (material inherits from the grade row above); reproduced with marking, size range and strengths only.
- Row 8 (ASTM A449): Marking "ASTM A449" printed alone in the flattened first column for the 7/4 to 3 size range — the source's merged cells carry no separate grade/material on this line (material inherits from the grade row above); reproduced with marking, size range and strengths only.
- Row 11 (): Continuation size-range row (9/8 to 3/2) for the grade above — the source table's merged cells print no marking/grade/material on this line; values belong to the preceding grade row's second size range.
- Row 13 (): Continuation size-range row (9/8 to 3/2) for the grade above — the source table's merged cells print no marking/grade/material on this line; values belong to the preceding grade row's second size range.
- Row 15 (): Continuation size-range row (9/8 to 3/2) for the grade above — the source table's merged cells print no marking/grade/material on this line; values belong to the preceding grade row's second size range.
- Row 16 (): Source prints the A354 Grade BC material as "Weathering steel, quench and temper" while Grade BD two rows down is "Alloy steel, quench and temper" — Grade BC is normally alloy (or weathering for Type 3-style variants); reproduced as printed, verify material callout against ASTM A354.
- Row 17 (): Continuation size-range row (11/4 to 4) for the grade above — the source table's merged cells print no marking/grade/material on this line; values belong to the preceding grade row's second size range. The yield column is not printed for this size range.
Materials
- Grade material callouts are as printed on the chart (see specs); material certification — mill test report per EN 10204 3.1 or equivalent — is an RFQ line, not a chart value
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (US Bolt Grades & Strength Chart — SAE Grades 1–8.2 and ASTM A307/A449/A325/A354/A490, Minimum Strengths) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Why does a bolt's strength change with diameter inside one grade, and how do I read this chart correctly when specifying?
Because bigger bolts cannot reach the same strength per unit area with the same heat treatment and quench depth — the standards deliberately lower minimums in steps as diameter grows. That is why Grade 2 carries 55 ksi proof through 3/4 in and only 33 ksi from 7/8 in (at which point it is chemically and mechanically the Grade 1 set), and Grade 5 steps down from 85 to 74 ksi proof at 1 1/8 in. Reading the chart is therefore always a two-column lookup: find the grade, then the size range your diameter falls in — quoting "Grade 5, 85 ksi proof" for a 1 1/4 in bolt is wrong before the fastener is even made. The second reading discipline is the chart's grouping: several markings share one grade row (A307 over Grade 1; A449 over Grade 5's upper ranges; A325 mirroring Grade 5 across three material types) and the merged layout continues a grade across a second size-range line with only the strengths printed — those continuation rows are flagged on the table below. Third, treat the numbers as what the source says they are: minimums exceeded by 99 percent of fasteners, a population floor for design margins rather than a promise about any single bolt. And keep the chart inside its world: SAE/ASTM grades do not convert to ISO property classes by dividing — different test geometry, different proof-load definitions — so a joint spanning the two systems needs both sets of documents. Hardness ranges and torque values live outside this chart; bring them to RFQ with the grade and size callout.
What is the MOQ and lead time for bolts to these grades?
The minimum order quantity is 1,000–10,000 pieces depending on size. Stock items ship in 3–7 days; high-strength and custom parts in 15–25 days. Common grades and sizes are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support