Hardware stores use a mix of gauge numbers, fractions, and metric millimeters that can be confusing for DIYers and pros alike. Our Screw Size Converter translates standard wood and machine screw gauges into their physical decimal and fractional equivalents. Match your screws to the correct drill bit size and ensure a secure fit for your next woodworking or mechanical assembly project.
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Screw Size Converter
Convert screw gauge numbers to major diameter in inches and millimeters.
Screw Hardware Specs
Wood screw and sheet metal screw sizes are specified by gauge number. Machine screws use a similar numbering system for smaller sizes.
Major Dia (in)0.164
Major Dia (mm)4.17
Clearance Hole (mm)4.50
The Gauge Rule
For wood screws, the major diameter (D) in inches is equal to **(Gauge × 0.013) + 0.060**. This allows you to estimate sizes between common gauges.
Selection Tip
Always pre-drill a pilot hole slightly smaller than the root diameter of the screw to prevent splitting wood, especially in hardwoods or near edges.
About International Screw Size Converter
1
Enter Gauge
Select a standard screw gauge number.
2
See Metric
Check the equivalent decimal inches and millimeter diameter.
Key Features
Gauge to Diameter
Translates #2 through #24 screw gauges into their precise fractional inch measurements.
Metric Mapping
Instantly see the equivalent diameter in millimeters for use with international hardware.
Drill Bit Guide
Provides recommendations for pilot hole sizes to prevent wood splitting.
Frequently Asked Questions
The diameter in inches is roughly (Gauge x 0.013) + 0.060.
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