When you’re constructing your next project, using the correct size screws is key. A screw that’s too long or wide could split the wood and affect the strength of your structure. Incorrectly selecting a screw can cost you time and money. Luckily, understanding how to read screw sizes isn’t difficult.

Screws are typically labeled with a gage number and length. The number refers to the screw diameter, while the length is the length of the screw without the head – usually listed as a number plus a decimal. A screw’s length may also be noted by a number that refers to the spacing of its threads, known as its pitch. For example, a screw with a pitch of 12 inch has fine threads while a screw with a 34-inch pitch has coarse threads.

Once you know how to read screw sizes, you can select the right fasteners for your next project. For instance, finish screws are designed for attaching trim and molding, so they have smaller heads than standard wood screws. They are also tapered to allow you to insert them beneath the surface of the wood, leaving a tiny hole that can be filled with wood putty.

Other factors to consider include the type of material you’re screwing into and the weight it will support. A heavier application will require stouter screws with a lower gauge, while a light-duty job could use a screw with a higher gauge.  pilot hole for 5/16 lag screw