Wood Screw Pilot Hole Chart
Pick your screw gauge, get the three holes that matter — hardwood pilot, softwood pilot, clearance — in fractions or millimeters.
Verified against independent hand calculation · sources cited below
1/8″
Pilot · hardwood
3/32″
Pilot · softwood
11/64″
Clearance (shank)
| Gauge | Pilot (hardwood) | Pilot (softwood) | Clearance |
|---|---|---|---|
| #2 | 1/16″ | 3/64″ | 3/32″ |
| #4 | 5/64″ | 1/16″ | 7/64″ |
| #5 | 5/64″ | 1/16″ | 1/8″ |
| #6 | 3/32″ | 5/64″ | 9/64″ |
| #7 | 3/32″ | 5/64″ | 5/32″ |
| #8 | 1/8″ | 3/32″ | 11/64″ |
| #9 | 1/8″ | 3/32″ | 3/16″ |
| #10 | 9/64″ | 7/64″ | 3/16″ |
| #12 | 5/32″ | 1/8″ | 7/32″ |
| #14 (1/4″) | 11/64″ | 9/64″ | 1/4″ |
Typical published sizes for standard wood screws. Very hard or brittle stock (hard maple, exotics, near an edge): go one drill size up. Deep screws in softwood can skip the pilot in the bottom board entirely — the threads want something to bite.
Three holes, one strong joint
A properly drilled screw joint has a clearance hole in the top board (the shank spins freely), a pilot hole in the bottom board (sized so threads bite without splitting), and — for flat-heads — a countersink. The chart’s hardwood pilot tracks the screw’s root diameter; softwood gets one size less because the fibers compress out of the way.
When the chart bends
- Very hard stock (hard maple, hickory, most exotics): one drill size up, and wax the screw.
- Near an edge or end: pilot generously — splits start at fibers with nowhere to go.
- Long screws: pilot the full length; a half-depth pilot concentrates all the strain at the tip.
Frequently asked questions
Why drill different pilot sizes for hardwood and softwood?
Softwood compresses, so threads can carve their own way through a smaller pilot; hardwood doesn’t forgive — too small a pilot splits the board or snaps the screw. Rule of thumb: the hardwood pilot roughly matches the screw’s root (core) diameter; the softwood pilot runs one size smaller.
What is the clearance hole for?
The board the screw head sits on shouldn’t be gripped by the threads at all — the shank passes freely through the clearance hole so the screw can pull the two boards together. Skip it and the threads bridge both boards, holding them apart with a stubborn gap.
When can I skip the pilot hole entirely?
Small screws (#6 and under) in soft woods, far from edges — especially with modern self-drilling deck screws. Always pilot: hardwoods, any screw near an end or edge, brass screws (which twist off), and anything you can’t afford to split.
What about brass or stainless screws?
Both are much weaker than steel. Drill the full-depth pilot one size up from the chart, then pre-thread with a steel screw of the same size and back it out before driving the brass one. Wax on the threads helps everything.
Sources & further reading
- Typical published pilot/clearance sizes for standard wood screws, consistent across major woodworking references
- For production screws (deck, pocket-hole), the manufacturer’s printed guidance wins