A325 and A449 bolts are virtually identical in mechanical and chemical properties through 1” in diameter. However, there are a few important differences between the two grades.

The diameter range, configuration and mechanical properties above 1” in diameter are the main differences. A325 bolts have a diameter range from 1/2″ through 1-1/2”. The specification requires the fasteners to have a forged head on the bolt. Due to their application, they have a shorter thread length than a typical heavy hex bolt. These bolts are designed to be used in structural steel connections.

A448 bolts have a diameter range from 1/4″ through 3”. These bolts are not limited to a specific configuration and can be made in any form of fastener. The strength properties of A449 above 1” drop significantly compared to A325 which makes them an unsuitable substitute in larger diameters.