Free woodworking tool
Pilot Hole Calculator
Find a reference pilot-hole diameter and drill-bit size for common wood screws. Compare softwood and hardwood recommendations in inches and millimeters.
Select the numbered screw gauge.
Wood density and screw design can affect the best fit.
Both units are shown in the result.
Pilot hole is for the receiving piece; clearance lets the screw shank pass through the top piece.
Recommended reference pilot hole 0.086 in2.18 mm
Important: These are reference values for conventional wood screws, not a universal engineering specification. Screw geometry, thread design, wood species, moisture, edge distance, and manufacturer guidance can change the appropriate size. Test on scrap of the same material and follow the screw manufacturer’s instructions.
Wood screw pilot-hole chart
Choose a screw size from the table to load it into the calculator. The drill-bit labels are US numbered or fractional-inch sizes.
| Screw | Softwood pilot | Drill bit | Hardwood pilot | Drill bit | Shank أک | Countersink أک |
|---|
Reference source: Newport Fasteners — Pilot Hole & Drill Bit Sizing Chart. Drill-bit availability and manufacturer recommendations may vary.
How to use the calculator
Choose your wood screw gauge and the material you are drilling into. Select the hole purpose, then read the diameter in inches and millimeters. Use the chart as a starting reference rather than an exact guarantee for every screw or wood species.
What is a pilot hole?
A pilot hole is a smaller pre-drilled hole in the receiving piece of wood. It helps guide the screw and can reduce splitting, especially near an edge or in dense hardwood.
What is the difference between a pilot hole and a clearance hole?
A pilot hole is made in the piece that will hold the screw threads. A clearance hole is made in the top piece so the screw shank can pass through without the threads gripping that piece. A clearance hole is normally selected to suit the actual screw shank and the desired fit.
Should I always drill a pilot hole?
No. Some modern self-drilling or self-countersinking screws are designed for use without a separate pilot hole in certain materials. Follow the screw manufacturer’s instructions, especially with hardwoods, large screws, and work near board ends.
Why can recommended drill sizes differ?
Tables can be based on different screw designs, thread-root diameters, wood density, and fitting preferences. Use the instructions supplied with your actual fastener when available, and test the fit on scrap material.