Chart with drill bit sizes for pre-drilling

If your bits aren't marked with sizes, here's how to select a bit:

Hold the screw to the light or a white background, with the bit you plan to use in front of it. You should see screw threads sticking out past the bit, but the bit should hide the rest of the screw.

When you find the right size bit, store it with the box of screws so you know which one it is.

Hardware stores usually have a size gauge so you can take the bit there and have them ID the size. Buy a bulk pack of the commonly used sizes, because drilling with a dull bit is no fun.

Drill bit sizes for pre-drilling (most commonly used sizes in bold)

Screw Size
 

Pilot hole size for hardwoods*
 

Pilot hole size for softwood**
 

#1
 

3/64
 

1/32
 

#2
 

3/64
 

3/32
 

#3
 

1/16
 

3/64
 

#4
 

1/16
 

3/64
 

#5
 

5/64
 

1/16
 

#6
 

3/32
 

5/64
 

#7
 

3/32
 

5/64
 

#8
 

1/8
 

3/32
 

#9
 

1/8
 

3/32
 

#10
 

1/8
 

7/64
 

#11
 

5/32
 

9/64
 

#12
 

9/64
 

1/8
 

 * Solid birch, maple, oaks, mahogany, pecan, cherry, hickory etc. (the expensive stuff) The exception is southern yellow pine, which is a hard wood, especially when it's old.
** Plywoods, MDF, "white wood" construction lumber, pine, alder, fir, spruce, redwood
NOTE: Shipping pallets are usually "white wood", but if they are coming from outside the US, they may be made of some local species of hardwood.