What size screws for 3/4 inch plywood into 2x4?

#8 × 1-1/2 in or 1-5/8 in. Drill a 7/64 in pilot in the 2x4 (1/8 in in hardwood) and an 11/64 in clearance hole through the plywood.

Screw and Nail Size Calculator (Length, Gauge and Pilot Holes)

Which screw for 3/4 in into a 2×4? This calculator picks a wood screw length and gauge, or a common nail size, from the thickness of the two pieces, keeps the point from coming through, and gives the pilot hole for hardwood or softwood, the clearance hole for the top piece and the countersink. It uses the standard rules of thumb (screw length about twice the top piece, nail length about three times it) and the ASME and ASTM dimensions for the fasteners themselves.

Screw and nail size calculator

How it works

Screw length: about 2 × thickness of the piece being fastened, at least 5/8 in of thread into the base piece, and 1/8 in short of coming through unless you say it may
Gauge: #6 for stock up to 3/8 in, #8 up to 3/4 in, #10 up to 1-1/2 in, #12 beyond; nominal diameter = 0.060 + 0.013 × gauge (ASME B18.6.1)
Pilot hole: about the root diameter in hardwood and a size smaller in softwood, from the common chart; clearance hole just over the shank diameter so the screw does not thread the top piece
Nails: length about 3 × the top piece, rounded to the nearest common penny size (ASTM F1667) that will not come through

Worked example

Fastening a 3/4 in board to a 2×4 (1-1/2 in) in softwood, with the point hidden:

Fastener: Wood screw
Thickness of the piece being fastened: 0.75 in
Thickness of the piece it goes into: 1.5 in
Wood being screwed into: Softwood (pine, fir, cedar, poplar)
Can the point come out the back?: No: keep it hidden inside

The calculator gives:

Screw to use: #8 x 1-1/2"
Pilot hole in the base piece (softwood): 7/64" (0.1094 in, 2.8 mm)
Clearance hole in the top piece: 11/64" so the screw pulls the pieces together
Countersink: to the head diameter: about 21/64" for a flat head #8
Thread in the base piece: 3/4" of 1-1/2"
Rule used: Length about 2 x the top piece, at least 5/8" into the base, and 1/8" short of coming through

A #8 × 1-1/2 in wood screw: 3/4 in of thread in the 2×4, 3/4 in short of the back. Drill a 7/64 in pilot in the 2×4 and an 11/64 in clearance hole in the board. The same joint in oak would use a 1/8 in pilot and wax on the threads. For nails, a 6d (2 in) common nail is the closest that stays hidden; a 7d (2-1/4 in) is the three-times rule exactly if the point may come through.

Wood screw pilot and clearance holes

Gauge	Diameter	Pilot, hardwood	Pilot, softwood	Clearance
#4	0.112 in	5/64"	1/16"	7/64"
#5	0.125 in	3/32"	5/64"	1/8"
#6	0.138 in	7/64"	3/32"	9/64"
#7	0.151 in	7/64"	3/32"	5/32"
#8	0.164 in	1/8"	7/64"	11/64"
#9	0.177 in	9/64"	1/8"	3/16"
#10	0.19 in	9/64"	1/8"	3/16"
#12	0.216 in	5/32"	9/64"	7/32"
#14	0.242 in	3/16"	5/32"	1/4"

Diameters per ASME B18.6.1 (0.060 + 0.013 × gauge). Hole sizes are the commonly published chart values for tapered wood screws.

Notes and limits

These are joinery rules of thumb for furniture, cabinets and general carpentry. Structural connections (ledgers, joist hangers, decks) follow the fastener schedule in the code or the hardware maker’s instructions, not this page.
Modern self-drilling construction screws have their own pilot recommendations, usually none in softwood.
Drywall screws are brittle; use wood screws or construction screws for anything that carries load.
In hardwood, a pilot hole is not optional. Wax or soap on the threads roughly halves the driving torque.
Countersink until the head sits just below the surface; over-countersinking weakens the hold of the head.

Frequently asked questions

What size screws for 3/4 inch plywood into 2×4?

#8 × 1-1/2 in or 1-5/8 in. Drill a 7/64 in pilot in the 2×4 (1/8 in in hardwood) and an 11/64 in clearance hole through the plywood.

How long should a wood screw be?

About twice the thickness of the piece being fastened, with at least 5/8 in of thread in the base piece and the point at least 1/8 in short of coming through.

What size nail for 3/4 inch boards?

About three times the thickness, so 2-1/4 in (7d) if the point may come through the base piece, or 2 in (6d) if it must stay hidden inside a 2×4.

What is the pilot hole size for a #10 screw?

9/64 in in hardwood, 1/8 in in softwood, with a 3/16 in clearance hole for the shank.

Do I need a pilot hole in softwood?

For #8 and larger screws near an end or edge, yes, to stop splitting. Away from edges in pine you can often drive #6 and #8 screws without one.

Sources

Last reviewed: 26 September 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.