Wood Screw Size Chart & Pilot Hole Guide

The model, stated exactly

Gauge numbers name the shank diameter: #6 is 0.138 inches, #8 is 0.164, #10 is 0.190, #12 is 0.216, and #14 is 0.242. The pilot hole is drilled into the receiving piece at roughly the shank diameter minus the thread depth, so the threads bite into solid wood without wedging it apart. Softwood compresses, so it takes a smaller pilot than hardwood for the same gauge: one drill size smaller in every row of the chart. The clearance hole is drilled through the top piece only, at the full shank diameter (rounded to the nearest standard bit), so the screw shank slides through the top piece and the head pulls it tight against the lower piece. Metric equivalents are the nearest standard metric screw sizes: M3.5, M4, M4.5, M5, and M6.

The worked example, line by line

Setup: a #8 wood screw going into softwood.

Line 1 — shank. A #8 screw measures 0.164 inches (4.17 mm) across the shank.

Line 2 — pilot hole. Softwood takes the smaller pilot: 7/64 inch (2.78 mm), about 0.026 inches under the shank, leaving thread depth to bite.

Line 3 — clearance hole. The top piece gets 11/64 inch (4.37 mm), just over the shank, so the screw slides through and pulls tight.

Line 4 — the hardwood difference. The same #8 screw in hardwood takes a 1/8-inch (3.18 mm) pilot — one size up — because hardwood will not compress out of the screw's way.

The wood screw size chart (print this)

The rule to remember: pilot hole = shank diameter minus the threads. If you forget the chart, pick the bit just under the shank for softwood and one size up for hardwood, and you will land within one size of the right hole every time.

Try these

#10 in hardwood. Shank 0.190 inches; pilot 9/64 inch (3.57 mm), clearance 3/16 inch. A #10 is the workhorse for hinges and hardware, and hardwood is where it splits boards if you skip the pilot.

#6 in softwood. Shank 0.138 inches; pilot 3/32 inch (2.38 mm), clearance 9/64 inch. Trim screws are thin and the pilot is tiny, but skipping it still splits pine near an edge.

#12 in hardwood. Shank 0.216 inches; pilot 5/32 inch (3.97 mm), clearance 7/32 inch. At this size the pilot is not optional: driving a #12 into oak without one is a split board waiting to happen.

#14 in hardwood. Shank 0.242 inches; pilot 11/64 inch (4.37 mm), clearance 1/4 inch. Structural screws this size also want a countersink so the head sits flush without crushing the surface.

Output · formula · meaning

Who uses this

• The weekend DIYer hanging shelves: picks #10 and pine, and drills 1/8-inch pilots instead of splitting the shelf brackets' mounting rail.
• The cabinet maker fitting oak doors: picks #8 and hardwood, and drills 1/8-inch pilots so hinge screws seat without cracking the stile.
• The deck builder driving #12 screws: checks the hardwood row before driving into dense decking boards, where an undrilled screw splits the end grain.
• The furniture restorer matching old screws: measures an old screw's shank at 0.190 inches, reads #10, and drills the matching pilot instead of guessing.

Accuracy & limitations

These are standard woodworking values for plain wood screws in solid wood, and they assume a sharp bit and a straight hole. Plywood, MDF, and particleboard behave differently: MDF needs a pilot at or slightly above the softwood size and splits less, while plywood near an edge splits more and wants the hardwood size even in soft plies. Very dense tropical hardwoods may need a pilot a full size above the chart, and screws driven within an inch of an end or edge always want a pilot even when the chart says the wood is forgiving. Bit sizes are standard fractional bits; a metric bit set lands within a few hundredths of an inch of the same holes and works fine. Error policy: unknown gauges or materials are reported as errors rather than guessed.