National standards exist for wood quality, and these standards ensure that each species and type of wood is given a rating, called a “grade." The percentages of variation and characteristics of different woods completely depend on the set of standards by which every wood is judged. These standards are made by major trade associations and professional organizations.

While grading is usually concerned with hardness of a species, and thus its correlating amounts of hardwood and sapwood, some grades depend on the mix of the two. Woods like hickory, cherry, and many exotic woods have especially contrasting colors of heartwood and sapwood. These woods may be ordered and graded as mixed (sapwood and heartwood), sap-only (only sapwood) or no-sap (only heartwood).

Four general grades exist for categorizing many species of different woods. Classifications are based only on appearance, as the structural soundness of most woods in generally the same all around.

It is the level of aesthetic beauty that is graded and given a score, and it is by this standard that prices for wood are set. A higher grade means a higher price, and a lower grade means a lower price.

First grade or clear wood has to have a surface almost completely free of imperfections, such as knots, dents, marls, or other flaws. Light streaking, burling, or few pinholes may be allowed. Variations in color are ok, but sapwood content has to be extremely minimal and almost non-existent.

Second-grade or Select wood standards accept small, sound tighter knot marks and other small defects as long as they aren’t large. A small amount of sapwood is allowed, as are variations in color.

Third-grade or Common wood is allowed more defects than the previous two, as well as larger knots on the surface. They can have a higher amount of streaking, more variety in color, and a larger amount of sapwood.

Fourth-grade or Lower Common Grade is the lowest wood grade on the scale, and is limited to very little. There may be large knots, heavy grain and surface imperfections, and great differences in color and large amounts of sapwood. It is often described as “rustic," and is common because of that quality.