Pilot Hole Size Chart
Right drill bit, first time. Select your screw size and wood type to get the pilot and clearance hole diameters.
Driving a screw without a pilot hole splits wood — and it's always the last piece. Drilling one too large kills the holding power. The pilot hole lets the threads bite; the clearance hole lets the shank slide freely through the top piece so the joint pulls tight.
Softwoods compress more easily and need a slightly smaller pilot hole. Hardwoods resist, so they need a bit larger hole to avoid splitting — especially near an end grain or edge.
Pilot Hole
Pilot hole
3/32″
0.0938″ · 2.4 mm
Clearance hole
9/64″
0.1406″ · 3.6 mm
Two holes, two jobs
- Pilot hole — drilled in the bottom piece (the one receiving the screw). Sized for the threads to bite without splitting. Smaller in softwood, larger in hardwood.
- Clearance hole — drilled in the top piece (the one being clamped). Sized so the shank passes through freely. Without it, the screw pushes the two pieces apart instead of pulling them together.
Full reference table
| Screw | Pilot (soft) | Pilot (hard) | Clearance |
|---|---|---|---|
| #2 | 1/16″ 1.6 mm | 1/16″ 1.6 mm | 3/32″ 2.4 mm |
| #4 | 1/16″ 1.6 mm | 5/64″ 2.0 mm | 7/64″ 2.8 mm |
| #6 | 5/64″ 2.0 mm | 3/32″ 2.4 mm | 9/64″ 3.6 mm |
| #8 | 3/32″ 2.4 mm | 7/64″ 2.8 mm | 11/64″ 4.4 mm |
| #10 | 7/64″ 2.8 mm | 1/8″ 3.2 mm | 3/16″ 4.8 mm |
| #12 | 1/8″ 3.2 mm | 9/64″ 3.6 mm | 7/32″ 5.6 mm |
| #14 | 9/64″ 3.6 mm | 11/64″ 4.4 mm | 1/4″ 6.4 mm |
Tips
- Near edges or end grain, go one size up on the pilot hole — these are the highest-split-risk spots.
- Countersinking is separate from pilot drilling. An 82° countersink bit sized to the screw head is standard for flathead screws.
- Self-tapping screws (pocket screws, sheet metal screws) have their own pilot hole requirements — these sizes are for standard wood screws.
- When in doubt, test on scrap of the same species before committing to your workpiece. You have scrap.
Useful gear
- Combination pilot/countersink bits — pilot hole and countersink in one pass, sized by screw number
- Brad point bit set — cleaner entry holes in hardwood than standard twist bits
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