Wood Screw Gauges

Wood screw gauges define the diameter and size of screws, with this chart showing metric equivalents of common imperial screw sizes, including head diameter, shank size, pilot hole sizes and masonry drill recommendations.

This reference is useful for joiners, carpenters, fabricators, installers and DIY users who need to choose the correct screw, pilot hole or drill size for timber and wall fixings.

How to Use This Wood Screw Gauge Chart

This wood screw gauge chart converts traditional imperial screw gauge numbers into metric sizes, helping you compare screw diameters, drill sizes and fixing requirements.

• Gauge number – indicates screw diameter; higher numbers generally mean a larger screw
• Head diameter – the approximate diameter of the screw head
• Shank diameter – the main body diameter of the screw
• Clearance drill size – the drill size used where the screw should pass through freely
• Pilot hole sizes – recommended drill sizes for softwood and hardwood
• Masonry drill size – suggested drill size when using wall plugs

Using the correct pilot hole and clearance drill size helps prevent timber from splitting, improves fixing strength and gives a cleaner, more accurate installation.

What Is a Wood Screw Gauge?

A wood screw gauge is a numerical sizing system used to indicate the diameter of a screw. Unlike sheet metal gauge systems, where higher numbers usually mean thinner material, wood screw gauges work the other way around: higher screw gauge numbers indicate larger screw diameters.

For example:

• Gauge 4 screws are typically used for lighter-duty applications
• Gauge 8 screws are common general-purpose wood screws
• Gauge 12 and above are used for heavier fixings and structural applications

As a useful guide, a Gauge 8 screw is approximately 4mm in diameter, making it one of the most widely used sizes in general woodworking and construction.

Wood Screw Gauge Chart: Metric, Pilot Holes, Plugs and Drill Sizes

The table below provides a practical reference for wood screw gauge sizes, including metric equivalents, head and shank diameters, pilot hole sizes and masonry drill recommendations.

Related Gauge Charts and Metal Resources

To complement this wood screw gauge chart, we also provide a useful sheet metal gauge chart showing sheet metal thicknesses from 1 thou to 1/2 inch, with conversions into millimetres and inches.

Metal Sheets Ltd supplies a wide range of sheet metals including aluminium, brass, copper, stainless steel, Corten steel and zinc for fabrication, interiors and design applications.

For smaller cut-to-size pieces and part sheets, visit our Metal Offcuts store. For bespoke fabrication or project enquiries, please contact Metal Sheets Ltd.

In this image: Vernier caliper measuring screw diameter for gauge reference.