The Janka hardness test is the international standard for measuring the resistance of a sample of wood to denting and wear.
It's expressed in psi, or pounds-per-square-inch. The test measures the pressure required to embed an 11.28mm (.444 in) diameter steel ball into wood to half the ball's diameter. The measurement was developed to determine whether a species is suitable for use as flooring; however, we include it here and compare it to the rating of red oak to help you make a buying choice.
There is a difference between hardness and being difficult to work with. Generally speaking, the harder the wood the easier it is to finish and polish. Harder woods create good, solid long-lasting joinery in furniture.
The hardness of wood varies with the direction of the wood grain, and varies from piece to piece. So a Janka rating is an average of numerous tests performed on all directions and numerous pieces. Use the Janka hardness rating as guide, not a definitive answer.
