Why do I need a pilot hole?

Pilot holes prevent wood from splitting, especially near edges and in hardwood. They also make driving screws easier and reduce the risk of the screw snapping. In softwood, a pilot hole is recommended; in hardwood, it is essential.

What is a clearance hole?

The clearance hole is drilled in the top piece of wood (the piece being fastened). It allows the screw shank to pass through without gripping, so the screw pulls the top piece tight against the bottom piece.

Do I always need a countersink?

For countersunk screws (the most common type), yes. The countersink allows the screw head to sit flush with or below the wood surface. Skip the countersink only if using pan-head or round-head screws.

WoodCalcs

Drill Bit Size Calculator — Screw Pilot Holes

Find the correct drill bit size for screws, dowels, and pilot holes in wood.

Screw Gauge

Wood Type

How We Calculate This

Pilot hole sizes depend on screw gauge and wood type. Hardwood needs larger pilot holes than softwood because it is denser and more likely to split.

Pilot hole: Slightly smaller than the screw root diameter
Clearance hole: Matches the screw shank diameter
Countersink: Matches the screw head diameter

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.