Ipe: 3670 Janka [Hardness] Rating vs.  1155 teak rating
Curupay: 3880 Janka [Hardness] Rating vs. 1260 Red Oak rating
Grapia: 2053 Janka [Hardness] Rating vs. 900 Cedar rating

A measure of the hardness of wood, produced by a variation on the Brinell hardness test. The test measures the force required to push a steel ball with a diameter of 11.28 millimeters (0.444 inches) 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). In Janka's original test. The results were expressed in unit of pressure, but when the ASTM standarized the test (tentative issue in 1922, standart frist formally adopted in 1927), it called for results in units of force
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The results are stated in various ways in different countries, which can lead to confusion, especially since the name of the actual unit employed is often not attached. In the United States, the measirement is in pounds-force. In Sweden it is aparently in kilogram-force (kgf), and in Australia, Janka hardness rating are either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, e.g. "360 janka".

The harness of woods usally varies with the direction of the grain. If testing is done on the surface of a plank, with the force exerted perpendicular to the grain, the test is said to be of "side hardness." Side hardnesses of a block of wood measured in the direction of the tree's center (radually), and on a tangent to the tree´s rings (tangentially), are typically very similar. End testing is also sometimes done (that is, testing the cut surface of a stump would be a test of end hardness). The side hardness of teak, for example, is in the range 3730 to 4800 newtons, while the end hardness is in the range 4150 to 4500 newtons.

The most common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring.

Wood Flooring Species Chart- Domestic & Exotic/ Imported