Lag Bolts vs. Lag Screws: What's the Difference?

Lag Bolts vs. Lag Screws: What's the Difference?

Lag bolts, also commonly known as lag screws, are some of the toughest fasteners out there. Used primarily for fastening into heavy lumber, these extremely sturdy fasteners withstand some of the most intense loads. The two terms "lag bolts" and "lag screws" are used interchangeably to refer to the same type of fastener. And for some, this causes plenty of confusion over saying the correct term.

So why do people use both lag bolts and lag screws when talking about the same thing? We explain further below as well as which one is the right phrase to use.


Why Do Lag Bolts & Lag Screws Mean the Same Thing?

The short answer to this question is this: it all boils down to the uniqueness of the lag itself.

People use lag bolts or lag screws to say the same thing because these fasteners exhibit characteristics of both a bolt and a screw. Traditionally, bolts are assembled with a nut and have machine threading, while screws are fastened by turning the head and having threads cut into the material. However, due to the design and function of these fasteners, lag bolts (or lag screws) are able to take on traits from both types.

Lag Bolt Characteristics:

  • Thickness: Lag bolts offer strong and durable fastening solutions due to their thick shafts and coarse threads, a feature similar to most bolts. This makes them incredibly easy to install and reliable for heavy-duty applications.

  • Hexagonal Heads: These fasteners also feature thick hexagonal heads without any slots notched into the top surfaces for screwing. Because of this, lag bolts require fastening from a torque wrench or impact wrench to keep them nice and tight into the material.

  • Self-Tapping: Most screws are considered self-drilling due to their sharp point and cutting thread design. However, the design of a lag bolt requires pre-drilled holes in order to fasten them properly. This means that they are actually self-tapping screws, instead.

  • No Washers: Unlike bolts, these fasteners do not use washers and are tightened by turning the head of the screw. The coarse threads of lag bolts cut through the material and hold firm when tightened.


two stainless steel lag bolts

    Lag Bolts vs. Lag Screws: Which is Correct?

    So after analyzing the characteristics of a bolt and a screw, which term is the correct one to use for these fasteners?

    Technically speaking, lags should be referred to as "screws," not "bolts." Part of the reason why is because you don't need a nut to fasten these products. They also look more similar to screws due to their tapered points. Nevertheless, it all depends on the person and their preferred name for these fasteners.

    No matter what you call them, or how you use them, lag bolts are easy to install and incredibly reliable for heavy duty materials. Fasteners Plus offers Conquest Lag Bolts made from a variety of high-strength steel options - 316 stainless steel, 304 stainless steel, and hot-dipped galvanized carbon steel - perfect for both interior and exterior applications. Talk with one of our product experts today to learn more about our selection and find the right lag bolts for your needs.


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    Fasteners Plus carries a variety of screws, connectors, anchors, nails, power tools, and more! Place your orders at and our dedicated team will get quality products sent to you. If you have any questions about fastener options, please do not hesitate to reach out to our Product Experts at (888) 794-1590 or by email at

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