Wood Screw Size Chart & Head Type Guide
Table of Contents
How do you know which wood screws are right for your project—and which size will fit your wood when all you have are measurements? Choosing the right wood screws can be a confusing process, but in this guide, we’ll help by taking a close look at the different types and uses of wood screws, including how to properly size them for your needs. You'll also find convenient tables below that you can reference later to better understand wood screw sizing and head types.
Wood Screw Size Chart
The size of a wood screw is generally determined by its gauge (or thickness/diameter) and the length of its shaft. However, wood screw sizes can be confusing if you're not already familiar with them because they use a gauge system with numbered sizes (e.g., #8 and #9 screws) rather than measurements. Both wood screw lengths and wood screw diameters may be measured in inches (actual size), but the gauge uses a screw size number. When shopping for wood screws, you'll typically see them marked with the gauge as a screw size number and the length in inches—for example, #4 x 1" long.
| Wood Screw Sizing Table | |||
|---|---|---|---|
| Screw Size | Closest Fractional Size |
Hard Wood Straight Pilot Bit |
Soft Wood Straight Pilot Bit |
| 2 | 3/32" | 1/16" | 1/16" |
| 3 | 7/64" | 5/64" | 1/16" |
| 4 | 7/64" | 5/64" | 1/16" |
| 5 | 1/8" | 3/32" | 5/64" |
| 6 | 9/64" | 7/64" | 3/32" |
| 7 | 5/32" | 7/64" | 3/32" |
| 8 | 5/32" | 1/8" | 7/64" |
| 9 | 11/64" | 9/64" | 1/8" |
| 10 | 3/16" | 9/64" | 1/8" |
| 12 | 7/32" | 5/32" | 9/64" |
| 14 | 1/4" | 11/64" | 5/32" |
| 16 | 17/64" | 3/16" | 11/64" |
| 18 | 19/64" | 7/32" | 13/64" |
| 20 | 5/16" | 15/64" | 7/32" |
In the wood screw size chart above, the column labeled “closest fractional size” relates to screw size (or gauge) and references the closest fractional diameter (in inches) of the corresponding screw shaft. The other two columns are designed to help you determine which drill bit to use when drilling a pilot hole for that screw size, with options for both hard and soft woods.
When it comes to choosing the right length for your wood screws, remember that longer screws will create a stronger joint—but screws must not be too long or they’ll break through the opposite side. Similarly, a thicker screw is stronger, but too much thickness can lead to splitting. When it comes to choosing the right wood screws, you may also want to consider the type of wood you’re using and whether you plan to drill a pilot hole first.
Different Types of Wood Screws
For the most part, the head types or shapes of wood screws are either flat, round, or oval, but other options do exist.
| Types of Wood Screws | ||
|---|---|---|
| Flat Head | Oval Head | Round Head |
 |  |  |
| Flat head screws have a flat top and a conically shaped underside. This allows the wood screw to sit flush with the finished workpiece, creating a smooth surface. | Oval head screws have the same conically shaped underside as flathead screws, but with a decorative top that protrudes slightly above the surface. | Round head screws are flat on the underside of the head, with a domed top that sits above the surface of the workpiece. |
The most common drive types for wood screws are the everyday Phillips and slotted head styles, but many other types are available, including hex head, square head, Torx/star head, and Phillips square head screws.
Wood Screw Materials
The most common wood screw materials are carbon steel and brass (for indoor applications) and stainless steel (for outdoor use). Outdoor wood screws are frequently treated with a coating (by electroplating or galvanizing) to prevent corrosion and deterioration.
Many manufacturers have developed their own proprietary coatings, most often for deck screws. Screws may also be coated with different finishes (e.g., bronze, nickel, or black oxide) for aesthetic or decorative reasons.
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Wood screws have stood the test of time, and their versatility means they’re probably not going away anytime soon. No matter what your needs are, Zoro’s excellent selection of wood screws can help you realize your woodworking dreams. While you’re shopping, don’t forget to check out our full selection of other useful fasteners, too.
Product Compliance and Suitability
The statements contained in this guide are intended for general informational purposes only. Such statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness, or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand, and follow all manufacturer instructions.
