Learning Center - Hardwood Janka Hardness Rating
Janka hardness ratings are a measure of the hardness of wood, produced by a variation on the Brinell hardness test. The test measures the force required to push a steel ball with a diameter of 11.28 millimeters (0.444 inches) into the wood to a depth of half the ball's diameter. The results are stated in various ways in different countries, which can lead to confusion, especially since the name of the actual units employed is often not attached. In the United States, the measurement is in pounds-force.
The most common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. Essentially this measures a wood's density and thus its dent resistance