The Janka Wood Hardness Scale
The Janka wood hardness test measures the resistance of a wood sample to denting and wear.
It measures the force required to embed an 11.2 millimeter (0.444 inch) diameter ball halfway into a wood sample. A common use of Janka hardness rating is to determine whether a species is suitable for use as wood flooring.
The chart is not to be considered an absolute; it is meant to help understand which woods are harder than others and to help you find the right wood for your flooring project.