4/4, 5/4, 6/4, 8/4, 12/4...?

These fractions refer to the rough thickness of any given lumber in terms of quarters of inches.  For example, 4/4 reads "four-quarters".  Four quarters of an inch equals one (4/4=1).  According to the National Hardwood Lumber Association (http://www.natlhardwood.org), the thickness of lumber is indicated by these fractions. 

• 4/4=1"
• 5/4=1-1/4"
• 6/4=1-1/2"
• 8/4=2"
• 12/4=3"

Since we have had all of our rough lumber surfaced on 2 sides, the actual thickness will be less than the last full quarter of an inch:

• 4/4 measures 13/16" or greater
• 5/4 measures 1-1/16" or greater
• 6/4 measures 1-5/16" or greater
• 8/4 measures 1-13/16" or greater
• 12/4 measures 2-13/16" or greater