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The ASTM A325 specification covers high strength heavy hex structural bolts from 1/2" diameter through 1-1/2" diameter. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. Refer to the Structural Bolts page of our site for thread lengths and other related dimensions.

This specification is applicable to heavy hex structural bolts only. For bolts of other configurations and thread lengths with similar mechanical properties, see Specification A 449.

Bolts for general applications, including anchor bolts, are covered by Specification A 449. Also refer to Specification A 449 for quenched and tempered steel bolts and studs with diameters greater than 1-1/2" but with similar mechanical properties.


TYPE 1 Medium carbon, carbon boron, or medium carbon alloy steel.
TYPE 2 Withdrawn November 1991.
TYPE 3 Weathering steel.
T Fully threaded A325. (Restricted to 4 times the diameter in length)
M Metric A325.

Connection Types

SC Slip critical connection.
N Bearing type connection with threads included in the shear plane.
X Bearing-type connection with threads excluded from the shear plane.

Mechanical Properties

SizeTensile, ksiYield, ksiElong. %, minRA %, min
1/2 - 1 120 min 92 min 14 35
1-1/8 - 1-1/2 105 min 81 min 14 35

Chemical Properties

Type 1 Bolts
ElementCarbon SteelCarbon Boron SteelAlloy SteelAlloy Boron Steel
Carbon 0.30 - 0.52% 0.30 - 0.52% 0.30 - 0.52% 0.30 - 0.52%
Manganese, min 0.60% 0.60% 0.60% 0.60%
Phosphorus, max 0.040% 0.040% 0.035% 0.035%
Sulfur, max 0.050% 0.050% 0.040% 0.040%
Silicon 0.15-0.30% 0.10 - 0.30% 0.15 - 0.35% 0.15 - 0.35%
Boron   0.0005 - 0.003%   0.0005 - 0.003%
Alloying Elements     * *
* Steel, as defined by the American Iron and Steel Institute, shall be considered to be alloy when the maximum range given for the content of alloying elements exceeds one of more of the following limits: Manganese, 1.65%, silicon, 0.60%, copper, 0.60%, or in which a definite range or a minimum quantity of any of the following elements is specified or required within the limits of the recognized field of constructional alloy steels: aluminum, chromium up to 3.99%, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium or any other alloying elements added to obtain a desired alloying effect.

Recommended Nuts and Washers

Type 1Type 3Type 1Type 3
A563C, C3, D, DH, DH3 A563DH A563C3, DH3 F436-1 F436-3
Note: Nuts conforming to A194 Grade 2H are a suitable substitute for use with A325 heavy hex structural bolts. The ASTM A563 Nut Compatibility Chart has a complete list of specifications.