1 fbm (foot board measure) is equal to a board 12" wide x 12" long x 1" thick.  Fbm is calculated as thickness (inches) x width (inches) x length (feet) / 12.

• Thickness and width used in the fbm calculation are nominal (2x4, 2x6) although the finished size may be 1.500 x 3.500, 1.500 x 5.500, etc.
• A 2x4x8' would equal 5.33 fbm

Lumber green target size must allow for:

• Sawing deviation - this can vary by equipment (+/- 0.015" to +/- 0.040")
• Shrinkage - varies by species and moisture content
• Planing - <.050" per face (varies with sawing deviation)

Green target sizes will have a direct effect on lumber recovery.  Reducing saw kerf and sawing deviation will allow decreased green target sizes which will increase lumber recovery.

Net lumber recovery for a 1st quartile northern softwood sawmill with an average log top diameter of 6.0" (15 cm) could be up to 304 fbm/m3 or 8.6 fbm/ft3 or .47 m3/m3.  Log quality, target sizes, saw kerfs and wane allowances will all effect maximum lumber recovery.  In this example the fiber recovery distribution is:

• Finished lumber (kds4s) 47%
• Chips 34%
• Sawdust & chip fines 9%
• Shrinkage 4%
• Shavings 6%

Lumber recovery generally increases as the log size increases.  The graph shows the relationship between log size (top diameter) and lumber recovery.

• For FBM/M3 multiply FBM/FT3 by 35.3
• For M3/M3 multiply FBM/FT3 by .065 (rough green production)
• For Diameter in CM multiply Inches by 2.54