What size pilot hole do I need for a #8 screw?

For a #8 screw use a 7/64 inch pilot hole in softwood and a 1/8 inch pilot hole in hardwood. The clearance hole in the top piece should be 11/64 inch. For a flush finish with a flat-head screw use a 7/16 inch countersink. These sizes apply to standard #8 wood screws - structural screws may need slightly different sizing.

What happens if the pilot hole is too big or too small?

Too small and the wood splits as the screw forces material outward - especially in hardwood and near edges. Too large and the threads have nothing to bite into - the screw spins without gripping and pulling out easily. The pilot hole should be sized to the root diameter of the screw thread, not the outer thread diameter.

Do I need a clearance hole for wood screws?

Yes for proper clamping action. Without a clearance hole in the top piece the screw threads grip both pieces and jack them apart instead of clamping them together. This is especially important for face frame assembly, drawer construction, and any joint where tight glue-line contact is needed. Drill a clearance hole slightly larger than the screw shank diameter.

What is the pilot hole size for a #10 deck screw?

For a #10 deck screw use a 9/64 inch pilot hole in both softwood and hardwood. Always pilot drill near board ends within 1 inch and near edges to prevent splitting. Pre-drill clearance holes through the top board using a 3/16 inch bit so the screw can clamp the decking down to the joist rather than lifting it.

Do I need a pilot hole for self-tapping screws?

Self-drilling screws (Tek screws with a drill point) do not need a pilot hole in metal - the tip drills its own hole. Self-tapping screws (no drill point) do require a pilot hole sized to the root diameter of the thread. For wood screws marked self-tapping you still need a pilot hole in hardwood and near edges in softwood.

Pilot Hole Size Chart for Screws: Every Gauge, Every Material (2026)

Drilling the right pilot hole size is the difference between a screw that drives smoothly and one that splits the wood or strips the thread. Too small and the wood splits. Too large and the screw has nothing to grip. Here is the complete reference.

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Pilot Hole Size Chart — Wood Screws

Screw Gauge	Shank Dia.	Softwood Pilot	Hardwood Pilot	Clearance Hole	Countersink
#4	0.112"	3/64"	1/16"	1/8"	5/16"
#6	0.138"	5/64"	3/32"	9/64"	3/8"
#8	0.164"	7/64"	1/8"	11/64"	7/16"
#10	0.190"	9/64"	9/64"	3/16"	1/2"
#12	0.216"	5/32"	11/64"	7/32"	9/16"
#14	0.242"	11/64"	3/16"	1/4"	5/8"

Pilot Hole vs Clearance Hole vs Countersink — What Each Does

Pilot hole: Drilled in the receiving piece (the piece the screw grips). Sized smaller than the screw thread so threads cut into the wood. Prevents splitting.
Clearance hole: Drilled in the top piece (the piece being fastened). Sized larger than the screw shank so the screw slides through freely. Allows the screw to clamp the two pieces together — without it, the screw lifts the top piece instead of clamping it.
Countersink: Angled recess that allows a flat-head screw to sit flush with the surface. Match countersink angle to screw head angle (82 degrees for most standard screws).

When Do You Need a Pilot Hole?

Always in hardwood (oak, maple, ipe, cumaru) — hardwood will split without a pilot hole regardless of screw size
Within 1 inch of any edge in softwood or plywood — edge grain splits easily
For screws #10 and larger in softwood — large screws split softwood near edges
Not required for small screws (#6 and under) in the middle of softwood panels

Metric Pilot Hole Chart

Screw Size	Softwood Pilot	Hardwood Pilot	Clearance Hole
M3	1.5 mm	2.0 mm	3.5 mm
M4	2.0 mm	2.5 mm	4.5 mm
M5	2.5 mm	3.5 mm	5.5 mm
M6	3.0 mm	4.0 mm	6.5 mm
M8	4.0 mm	5.5 mm	9.0 mm
M10	5.0 mm	7.0 mm	11.0 mm

Where to Buy Drill Bits for Pilot Holes

Canada:

Home Depot CA → RONA → Amazon CA →

United States:

Home Depot US → Lowe's → Amazon US →

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Related Guides

Wood Screw Size Chart — Complete gauge to diameter reference
Deck Screws Complete Guide — Outdoor screw selection
Drill Bit Size for Concrete Anchors — Anchor pilot holes
Drill Bit Selector — Instant bit recommendation for any material
Screw Size Selector — Get your exact screw spec instantly