The policy of Wood and Fiber Science is to publish only in SI units. The “in-lb” (sometimes referred to as “US Customary”) units are not to be shown, even in parentheses after SI units.
When converting to SI, keep in mind several pitfalls:
Many wood products are produced in “nominal” sizes; in metric units, these must be described as actual sizes. Here are two examples:
Log sizes should be given in meters (m) in length and either cm or mm in diameter. In SI units the preference is always in multiples of powers of three: mm, m, km, etc. Conversion of panel production (ft2, 3/8 in. basis) should be expressed as m2, 10 mm basis.
Make sure the SI units have the same number of significant digits (as in the 2 x 4 example); if you are converting from a nominal dimension, for example, with a 10-ft log, it makes more sense to express this as a 3-m log rather than a 3.05-m log. This is an example of a “hard” vs a “soft” conversion. Wherever justified, the hard conversion (nicely rounded) should be used. Another example is converting temperature from ºF to ºC. If you have a conditioning chamber operating at 70ºF, you could express this as 21.1ºC (soft conversion) or 21ºC (hard conversion); the decision has as much to do with the effect of temperature on the materials in the chamber as the precision of the measurement and variation in actual temperature.