How do I convert to metric lumber sizes?

When converting lumber sizes the nominal dimensions (2x) or (4x) should NOT be converted, rather the actual sizes like 1.5"x3.5" should be soft converted to 38x89mm.

2x4 = 38x89mm
2x6 = 38x140mm
2x8 = 38x184mm
2x10 = 38x235mm
2x12 = 38x286mm

Soft vs. Hard conversion - soft conversion is simply converting inch-pound units to the nearest equivalent metric unit. Panel products for example are typically 4'x8' which would convert to 1220x2440mm. Hard conversion is when the metric units are rounded to a rational unit. In the preceding example hard conversion for panels would be 1200x2400.

To convert from board feet to cubic meters; according to ASTM E380, multiply board feet by 0.002359737.

See eCourse MAT 120 Metric and Wood for more information.