Pilot Hole Calculator

1. Select the screw gauge from the dropdown. The gauge number is printed on the screw box (common sizes are #6, #8 and #10).
2. Choose softwood (pine, cedar, spruce, fir) or hardwood (oak, maple, walnut, cherry).
3. Read the pilot hole size as a fractional inch and a decimal equivalent.
4. Note the clearance hole size for the top board so the screw pulls the joint tight.

Here is what each result line means:

A pilot hole is a small-diameter hole drilled into wood before driving a screw. It serves three purposes: it prevents the wood from splitting, it makes the screw easier to drive, and it helps the screw follow a straight path into the workpiece.

The pilot hole diameter should approximately match the root diameter of the screw threads (the solid core between the thread ridges). A hole that is too small still risks splitting; a hole that is too large reduces the holding strength of the threads.

The calculator uses a standard reference table that maps each wood screw gauge number to four diameters:

• Shank diameter — the outside diameter of the unthreaded shank.
• Softwood pilot — the recommended pilot hole for pine, cedar, spruce and similar species.
• Hardwood pilot — the larger pilot needed for oak, maple, walnut and similar dense species.
• Clearance hole — the hole in the top board that lets the screw pass through without threading.

Hardwood pilot holes are larger because dense grain is more prone to splitting. Softwood is more forgiving, so the pilot can be slightly smaller, which gives the threads more wood to grip.

1. Look up the screw gauge in the reference table.
2. Select the softwood or hardwood column based on the workpiece species.
3. Report the pilot diameter in fractional and decimal inches.
4. Report the clearance hole and shank diameter for reference.

Driving a #8 wood screw into red oak (hardwood).

Step 1. Look up gauge #8 in the table: shank = 0.164 in, hardwood pilot = 1/8 in (0.125 in), clearance = 11/64 in (0.172 in).

Step 2. Chuck a 1/8 in drill bit and drill the pilot hole into the oak piece.

Step 3. If fastening two boards, drill the top board with an 11/64 in clearance hole so the screw pulls the joint tight.

Step 4. Drive the #8 screw. The 1/8 in pilot prevents the oak from splitting while letting the threads grip.

Wood Species and Density

The single biggest factor is whether the wood is softwood or hardwood. Dense tropical hardwoods like ipe or jatoba may need a pilot hole one size larger than the standard hardwood recommendation. Very soft species like balsa or western red cedar may need no pilot at all for small screws.

Screw Gauge and Length

Larger gauge screws displace more wood and need larger pilots. Longer screws increase the friction along the shank, making a pilot even more important.

Proximity to Edges and Ends

Screws driven within 2 inches of a board edge or end grain are far more likely to split the wood. Always drill a pilot hole near edges, even in softwood.

Screw Type

Self-drilling screws with a split point may skip the pilot in softwood, but a pilot is still recommended in hardwood or near edges. Traditional slotted and Phillips-head screws always benefit from a pilot.

Moisture Content

Dry wood (below 12% MC) splits more easily than green wood. If you are working with kiln-dried hardwood, do not skip the pilot hole.

Complete reference table for wood screw gauges #2 through #14.

Source: standard wood screw pilot hole charts (Blacksmith Bolt, Workshop Calc).

This table compares pilot hole sizes across all standard gauges so you can see how the pilot, shank and clearance hole scale with screw size.

For gauges #2 through #5, the softwood and hardwood pilots are the same or very close. Starting at #6, hardwood pilots are consistently about 1/64 in (0.016 in) larger than softwood pilots. This difference matters most in dense species like white oak and hard maple.

Hardwood Furniture and Cabinetry

Oak, maple and walnut split easily. Every screw in a hardwood project needs a pilot hole.

Near Board Edges and End Grain

Screws within 2 inches of an edge or driven into end grain are at high risk of splitting. Drill a pilot even in soft pine.

Thin Stock

Boards thinner than 1/2 inch (12 mm) are prone to splitting regardless of species. Always pre-drill in thin material.

Finish Work and Trim

Baseboard, casing and molding are visible surfaces where a split ruins the piece. A pilot hole also helps the screw sit flush or countersink cleanly.

1. Skipping the Pilot in Hardwood

Hardwood looks strong, but it splits along the grain under screw pressure. A pilot hole is not optional in oak, maple, cherry or walnut.

2. Using the Wrong Size Drill Bit

A pilot that is too small still splits the wood. A pilot that is too large strips the threads and weakens the joint. Match the bit to the chart.

3. Forgetting the Clearance Hole

The clearance hole in the top board lets the screw pull the two pieces together. Without it, the screw threads grip both boards and the joint stays loose.

4. Drilling Too Deep

The pilot hole should be slightly shorter than the screw length so the threads bite at the tip. Mark the depth on the bit with tape.

5. Not Drilling Near Edges

Any screw within 2 inches of a board edge or end should have a pilot, even in softwood. Edge splits are the most common fastening failure in woodworking.

The calculator uses standard pilot hole reference tables rounded to the nearest common fractional drill bit size.

For a #8 wood screw, drill a 7/64 in (0.109 in) pilot hole in softwood or a 1/8 in (0.125 in) pilot hole in hardwood.

In hardwood, yes. In softwood, you can sometimes skip the pilot for small screws (#6 and below) driven away from edges, but a pilot always gives a cleaner result.

A pilot hole is a small hole in the piece that receives the screw threads. A clearance hole is a larger hole in the top board that lets the screw shank pass through without gripping, so the screw pulls the joint tight.

Going one size up reduces holding strength. Only do this in very dense exotic hardwoods that still split with the standard pilot.

Plywood resists splitting better than solid wood, but a pilot is still recommended near edges or for screws #8 and above to prevent surface tearout.

Use the next smaller standard bit. A slightly undersized pilot is better than no pilot and better than one that is too large.

Drill to about 80 to 90 percent of the screw length. Mark the depth on the drill bit with a piece of tape.

Self-drilling screws with a split point can skip the pilot in softwood away from edges. In hardwood, a pilot is still recommended.

The #8 screw is the most widely used gauge for general woodworking, cabinetry and furniture. The #6 is common for trim and light duty work.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Blacksmith Bolt, Pilot Hole Chart for Wood Screws (complete pilot hole, shank and clearance hole table by gauge).
• Workshop Calc, Pilot Hole Chart (softwood and hardwood pilot sizes for standard screw gauges).
• Fine Power Tools, What Size Drill Bit for a Screw (practical guide to matching drill bits to screw sizes).