A measure of the hardness of wood. The test measures the force required to push a steel ball with a diameter of 11.28 millimeters into the wood to a depth of half the ball’s diameter (the diameter was chosen to produce a circle with an area of 100 square millimeters). Red Oak, which has a Janka rating of 1290, is the industry benchmark for comparing the relative hardness of different wood species. However it is a benchmark only. Not the “standard” to which all wood should perform. There are many floors in service with a lower hardness rating that last for many years, if not 100 years or more.

Below is an illustration of what the JANKA test accomplishes (forcing a steel ball into a slat of wood) and the JANKA table which shows the rating of many wood species.