Wood Screw Pilot Hole Sizes
Screw Size	Body Dia.	Shank Pilot Hole*	Pilot Hole in Softwood	Pilot Hole in Hardwood
0	0.060	1/16	1/64	1/32
1	0.073	5/64	1/32	1/32
2	0.086	3/32	1/32	3/64
3	0.099	7/64	3/64	1/16
4	0.112	7/64	3/64	1/16
5	0.125	1/8	1/16	5/64
6	0.138	9/64	1/16	5/64
7	0.151	5/32	1/16	3/32
8	0.164	11/64	5/64	3/32
9	0.177	3/16	5/64	7/64
10	0.190	3/16	3/32	7/64
11	0.203	13/64	3/32	1/8
12	0.216	7/32	7/64	1/8
14	0.242	1/4	7/64	9/64
16	0.268	17/64	9/64	5/32
18	0.294	19/64	9/64	3/16
20	0.320	21/64	11/64	13/64
24	0.372	3/8	3/16	7/32

These dimensions are for standard American wood screws, which are tapered. They are not suitable for screws which are not tapered, such as dry wall screws. All dimensions are in inches.

* - The shank pilot hole is one which will clear the thickest part of the screw body.