The test involves measuring the force required to embed a .444” steel ball into wood to half its diameter. It is one of the best ways to determine the ability of a wood species to withstand denting and wear; and for that reason, one of the most common uses of the Janka hardness scale is to determine whether a species is suitable for use as flooring.
It is also a good indicator of how difficult it is to saw or nail hardwood flooring of a given species. Red Oak is the benchmark of the Janka scale. All other species are compared to it.
The following comparison chart illustrates the relative hardness of various species of wood flooring using the Janka scale. The grades are arranged from softest to hardest, and the number is the Janka rating for that particular grade of hardwood flooring.