Janka Hardness Scale
The Janka rating is a measurement of the amount of force it takes to push a .444” diameter steel ball half way into a test piece of wood. In other words it's a test to measure how resistant a wood is to denting.The most common use of the Janka rating is to determine the suitability a wood is for use in flooring. The higher the number the greater its resistance to denting it tends to be.For the installer it's a good way to determine how hard the wood might be to cut or nailed.
Below are a list of some of the more common and exotics woods that have been used in this area and their Janka rating.