Structural Bolt Reference
The ASTM bolt grades found on structural steel: what each is specified to carry and where each is used.
Grades
- ASTM A307
The low-strength general-purpose bolt (Grade A). Cheap and widely stocked. Use only where the connection design and specification permit it: handrail, grating clips, light framing, temporary work. Not interchangeable with F3125 structural bolts.
- ASTM A325
The default high-strength structural bolt for building steel. Now published as ASTM F3125 Grade A325, though every shop drawing and mill ticket in the field still says A325.
- ASTM A449ASTM high-strength fastener — not assigned AISC J3.2 Group A/B design values
An ASTM high-strength fastener, not an American Institute of Steel Construction (AISC) Group A or B structural bolt. Used where a high-strength bolt is needed outside the F3125 range: diameters over 1-1/2 in. and anchorage. AISC 360 designs it as a threaded part (Section A3.4, Table J3.2). Strength steps down with diameter.
- ASTM A490
The high-strength alloy bolt, one step up from A325. Published as ASTM F3125 Grade A490. Used where the connection needs the capacity, with the extra care its hardness demands.
Covers the grades common on structural steel drawings. ASTM F3125 also contains Grade 144 (144 ksi, added 2025) and the twist-off (tension-control) styles F1852 and F2280.
Allowable capacity, all grades
| Diameter | Ab (in²) | A307 tension (kip) | A325 tension (kip) | A490 tension (kip) | A307 shear (kip) | A325 shear (kip) | A490 shear (kip) |
|---|---|---|---|---|---|---|---|
| 1/2" | 0.196 | 4.4 | 8.8 | 11.1 | 2.7 | 5.3 | 6.7 |
| 5/8" | 0.307 | 6.9 | 13.8 | 17.3 | 4.1 | 8.3 | 10.4 |
| 3/4" | 0.442 | 9.9 | 19.9 | 25.0 | 6.0 | 11.9 | 15.0 |
| 7/8" | 0.601 | 13.5 | 27.1 | 34.0 | 8.1 | 16.2 | 20.4 |
| 1" | 0.785 | 17.7 | 35.3 | 44.4 | 10.6 | 21.2 | 26.7 |
| 1-1/8" | 0.994 | 22.4 | 44.7 | 56.2 | 13.4 | 26.8 | 33.8 |
| 1-1/4" | 1.227 | 27.6 | 55.2 | 69.3 | 16.6 | 33.1 | 41.7 |
| 1-1/2" | 1.767 | 39.8 | 79.5 | 99.8 | 23.9 | 47.7 | 60.1 |
Allowable Stress Design (ASD), Ω = 2.00. Bearing-type, snug-tight, one shear plane, threads included (N), nominal shank area. For end-loaded connections with a fastener pattern longer than 38 in., multiply shear by 0.833 per AISC 360 Table J3.2. Bearing, tearout, block shear, net section, prying and bolt interaction are separate checks. Fu is a material minimum, not an allowable stress.
Comparisons
Related tools
- Bolt Tensile & Shear Capacity Calculator
allowable tension and shear by grade, diameter and bolt count
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- Steel Grade Reference
ASTM specifications with yield and tensile strength