Wood Screw Pilot Hole Calculator

Summary

Enter screw gauge, wood type, and thickness to get the correct pilot hole drill bit size and countersink recommendation.

How it works

1. Select the screw gauge number — common sizes run from #2 (fine woodworking) to #20 (heavy structural work).
2. Choose the wood type: hardwood (oak, maple, walnut, cherry, etc.) requires a slightly larger pilot hole; softwood (pine, cedar, fir, spruce) can use a smaller one.
3. Enter the material thickness in inches to get a minimum screw length recommendation.
4. The calculator outputs the recommended pilot hole diameter in both fractional inches and millimeters.
5. A shank clearance hole size is also shown for the top board when joining two pieces.
6. Use the countersink size guidance to select the right countersink bit for a flush finish.

Use cases

• Avoiding wood splitting when driving screws near board edges or ends.
• Selecting the right bit before drilling into hardwoods like oak or maple.
• Assembling furniture and cabinets with flush-set wood screws.
• Pre-drilling pilot holes in softwood decking and framing.
• Teaching apprentice woodworkers the correct pre-drilling technique.
• Choosing a countersink bit to match a specific screw head diameter.
• Drilling pilot holes in thin stock to prevent blowout.
• Referencing screw dimensions when substituting a different gauge.

Frequently Asked Questions