The Janka hardness test (;[1] pronounced as /de/), created by Austrian-born American researcher Gabriel Janka (1864–1932), measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an 11.28mm steel ball halfway into a sample of wood. (The diameter was chosen to produce a circle with an area of 100 square millimeters, or one square centimeter.)[2]
A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. For hardwood flooring, the test usually requires an sample with a thickness of at least 6–8 mm, and the most commonly used test is the ASTM D1037. When testing wood in lumber form, the Janka test is always carried out on wood from the tree trunk (known as the heartwood), and the standard sample (according to ASTM D143) is at 12% moisture content and clear of knots.[3]
The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the grain, is said to be of "side hardness". Testing the cut surface of a stump is called a test of "end hardness". Side hardness may be further divided into "radial hardness" and "tangential hardness", although the differences are minor and often neglected.
The results are stated in various ways, leading to confusion, especially when the actual units employed are often not attached. The resulting measure is always one of force. In the United States, the measurement is in pounds-force (lbf). In Sweden, it is in kilograms-force (kgf), and in Australia, either in newtons (N) or kilonewtons (kN). This confusion is greatest when the results are treated as units, for example "660 Janka".[4]
The Janka hardness test results tabulated below followed ASTM D 1037-12 testing methods. Lumber stocks tested range from 1" to 2" (25-50 mm) thick. The tabulated Janka hardness numbers are an average. There is a standard deviation associated with each species, but these values are not given. No testing was done on actual flooring.
Other factors affect how flooring performs: the type of core for engineered floorings, such as pine, HDF, poplar, oak, or birch; grain direction and thickness; floor or top wear surface, etc. The chart is not to be considered an absolute; it is meant to help people understand which woods are harder than others.
| Key | |
|---|---|
| Hardwood | |
| Softwood | |
| Pseudowood |
| Force: pounds-force (newtons) | |||
| scope=row style="background:#ffe5e5;" | Australian Buloke[5] | ||
|---|---|---|---|
| scope=row style="background:#ffe5e5;" | Schinopsis brasiliensis, Quebracho, Barauna, Chamacoco[6] | ||
| scope=row style="background:#ffe5e5;" | Schinopsis balansae, Quebracho Colorado, Red Quebracho[7] | ||
| scope=row style="background:#ffe5e5;" | Lignum vitae, Guayacan, Pockholz | ||
| scope=row style="background:#ffe5e5;" | Anadenanthera colubrina var. cebil, Curupay, Angico Preto, Brazilian Tiger Mahogany | ||
| scope=row style="background:#ffe5e5;" | Snakewood, Letterhout, Brosimum guianense | ||
| scope=row style="background:#ffe5e5;" | Brazilian Olivewood | ||
| scope=row style="background:#ffe5e5;" | Brazilian Ebony | ||
| scope=row style="background:#ffe5e5;" | Ipê, Brazilian Walnut, Handroanthus lapacho | ||
| scope=row style="background:#ffe5e5;" | African Pearwood, Moabi | ||
| scope=row style="background:#ffe5e5;" | Grey Ironbark | ||
| scope=row style="background:#ffe5e5;" | Bolivian Cherry | ||
| scope=row style="background:#ffe5e5;" | Lapacho | ||
| scope=row style="background:#ffe5e5;" | Sucupira, Brazilian Chestnut, Tiete Chestnut | ||
| scope=row style="background:#ffe5e5;" | Kingwood[8] | ||
| scope=row style="background:#ffe5e5;" | Dipteryx, Cumaru, Brazilian Teak[9] | ||
| scope=row style="background:#ffe5e5;" | Ironwood | ||
| scope=row style="background:#ffe5e5;" | Ebony | ||
| scope=row style="background:#ffe5e5;" | Massaranduba, Brazilian Redwood, Paraju | ||
| scope=row style="background:#ffe5e5;" | Yvyraro | ||
| scope=row style="background:#e6e6ff;" | Strand Woven Bamboo | ||
| scope=row style="background:#ffe5e5;" | Cocobolo | ||
| scope=row style="background:#ffe5e5;" | Bloodwood (Brosimum rubescens) | ||
| scope=row style="background:#ffe5e5;" | Boxwood | ||
| scope=row style="background:#ffe5e5;" | Olive[10] | ||
| scope=row style="background:#ffe5e5;" | Red Mahogany, Turpentine | ||
| scope=row style="background:#ffe5e5;" | Live Oak | ||
| scope=row style="background:#ffe5e5;" | Southern Chestnut | ||
| scope=row style="background:#ffe5e5;" | Spotted Gum | ||
| scope=row style="background:#ffe5e5;" | Brazilian Cherry, Jatoba | ||
| scope=row style="background:#ffe5e5;" | Mesquite | ||
| scope=row style="background:#ffe5e5;" | Golden Teak | ||
| scope=row style="background:#ffe5e5;" | Guatambú, Kyrandy, Balfourodendron riedelianum | ||
| scope=row style="background:#ffe5e5;" | Santos Mahogany, Bocote, Cabreuva, Honduran Rosewood | ||
| scope=row style="background:#ffe5e5;" | Pradoo | ||
| scope=row style="background:#ffe5e5;" | Brazilian Koa | ||
| scope=row style="background:#ffe5e5;" | Brushbox | ||
| scope=row style="background:#ffe5e5;" | Osage Orange[11] | ||
| scope=row style="background:#ffe5e5;" | Karri | ||
| scope=row style="background:#ffe5e5;" | Sydney Blue Gum | ||
| scope=row style="background:#e6e6ff;" | Palmyra Palm | ||
| scope=row style="background:#ffe5e5;" | Bubinga | ||
| scope=row style="background:#ffe5e5;" | Cameron | ||
| scope=row style="background:#ffe5e5;" | Tallowwood | ||
| scope=row style="background:#ffe5e5;" | Merbau | ||
| scope=row style="background:#ffe5e5;" | Amendoim | ||
| scope=row style="background:#ffe5e5;" | Jarrah | ||
| scope=row style="background:#e6e6ff;" | Coconut Palm | ||
| scope=row style="background:#ffe5e5;" | Purpleheart | ||
| scope=row style="background:#ffe5e5;" | Goncalo Alves, Tigerwood | ||
| scope=row style="background:#ffe5e5;" | Hickory, Pecan, Satinwood | ||
| scope=row style="background:#ffe5e5;" | Afzelia, Doussie, Australian Wormy Chestnut | ||
| scope=row style="background:#ffe5e5;" | Castello boxwood | ||
| scope=row style="background:#ffe5e5;" | Bangkirai | ||
| scope=row style="background:#ffe5e5;" | Rosewood | ||
| scope=row style="background:#ffe5e5;" | Apple[12] | ||
| scope=row style="background:#ffe5e5;" | African Padauk | ||
| scope=row style="background:#ffe5e5;" | Blackwood | ||
| scope=row style="background:#ffe5e5;" | Merbau | ||
| scope=row style="background:#ffe5e5;" | Kempas | ||
| scope=row style="background:#ffe5e5;" | Black Locust | ||
| scope=row style="background:#ffe5e5;" | Highland Beech | ||
| scope=row style="background:#ffe5e5;" | Red Mulberry | ||
| scope=row style="background:#ffe5e5;" | Wenge, Red Pine, Hornbeam | ||
| scope=row style="background:#ffe5e5;" | Tualang | ||
| scope=row style="background:#ffe5e5;" | Zebrawood | ||
| scope=row style="background:#ffe5e5;" | True Pine, Timborana | ||
| scope=row style="background:#ffe5e5;" | Peroba | ||
| scope=row style="background:#fffde5;" | European Yew[13] | ||
| scope=row style="background:#ffe5e5;" | Sapele, Sapelli, Kupa'y | ||
| scope=row style="background:#ffe5e5;" | Curupixa | ||
| scope=row style="background:#ffe5e5;" | Sweet Birch | ||
| scope=row style="background:#ffe5e5;" | Hard maple, Sugar Maple | ||
| scope=row style="background:#ffe5e5;" | Caribbean Walnut | ||
| scope=row style="background:#ffe5e5;" | Kentucky coffeetree | ||
| scope=row style="background:#e6e6ff;" | Natural Bamboo (represents one species) | ||
| scope=row style="background:#fffde5;" | Australian Cypress | ||
| scope=row style="background:#ffe5e5;" | White Oak | ||
| scope=row style="background:#ffe5e5;" | Tasmanian oak | ||
| scope=row style="background:#ffe5e5;" | Ribbon Gum | ||
| scope=row style="background:#ffe5e5;" | Ash (White) | ||
| scope=row style="background:#ffe5e5;" | American Beech | ||
| scope=row style="background:#ffe5e5;" | Red Oak (Northern) | ||
| scope=row style="background:#fffde5;" | Caribbean Heart Pine | ||
| scope=row style="background:#ffe5e5;" | Keruing | ||
| scope=row style="background:#ffe5e5;" | Yellow Birch, Iroko | ||
| scope=row style="background:#ffe5e5;" | Movingui | ||
| scope=row style="background:#fffde5;" | Heart pine | ||
| scope=row style="background:#ffe5e5;" | Carapa guianensis, Brazilian Mesquite | ||
| scope=row style="background:#fffde5;" | Larch | ||
| scope=row style="background:#e6e6ff;" | Carbonized Bamboo (represents one species) | ||
| scope=row style="background:#ffe5e5;" | Teak | ||
| scope=row style="background:#ffe5e5;" | Brazilian Eucalyptus, Rose Gum | ||
| scope=row style="background:#ffe5e5;" | English Oak[14] | ||
| scope=row style="background:#ffe5e5;" | Makore | ||
| scope=row style="background:#fffde5;" | Siberian Larch | ||
| scope=row style="background:#ffe5e5;" | Peruvian Walnut | ||
| scope=row | Boreal | ||
| scope=row style="background:#ffe5e5;" | Black Walnut, North American Walnut | ||
| scope=row style="background:#ffe5e5;" | Cherry | ||
| scope=row style="background:#ffe5e5;" | Black Cherry, Imbuia | ||
| scope=row style="background:#ffe5e5;" | Red Maple[15] | ||
| scope=row style="background:#ffe5e5;" | Boire | ||
| scope=row style="background:#ffe5e5;" | Paper Birch | ||
| scope=row style="background:#fffde5;" | Eastern Red Cedar, Monkeypod | ||
| scope=row style="background:#fffde5;" | Southern Yellow Pine (Longleaf) | ||
| scope=row style="background:#ffe5e5;" | Lacewood, Leopardwood | ||
| scope=row style="background:#ffe5e5;" | African Mahogany | ||
| scope=row style="background:#ffe5e5;" | Mahogany, Honduran Mahogany | ||
| scope=row style="background:#fffde5;" | Parana | ||
| scope=row style="background:#ffe5e5;" | Sycamore | ||
| scope=row style="background:#ffe5e5;" | Box Elder | ||
| scope=row style="background:#ffe5e5;" | Shedua | ||
| scope=row style="background:#fffde5;" | Radiata Pine[16] | ||
| scope=row style="background:#ffe5e5;" | Silver Maple[17] | ||
| scope=row style="background:#fffde5;" | Southern Yellow Pine (Loblolly and Shortleaf) | ||
| scope=row style="background:#fffde5;" | Douglas Fir | ||
| scope=row style="background:#fffde5;" | Western Juniper | ||
| scope=row style="background:#ffe5e5;" | Alder (Red) | ||
| scope=row style="background:#fffde5;" | Larch | ||
| scope=row style="background:#ffe5e5;" | Chestnut | ||
| scope=row style="background:#ffe5e5;" | Yellow Poplar, Poplar | ||
| scope=row style="background:#fffde5;" | Hemlock | ||
| scope=row style="background:#fffde5;" | Western White Pine | ||
| scope=row style="background:#ffe5e5;" | Basswood | ||
| scope=row style="background:#fffde5;" | Eastern White Pine | ||
| scope=row style="background:#fffde5;" | Western Red Cedar | ||
| scope=row style="background:#ffe5e5;" | Cuipo | ||
| scope=row style="background:#ffe5e5;" | Balsa | ||
| scope=row style="background:#ffe5e5;" | Balsa, softest wood ever measured: single unusual example[18] |