Janka hardness

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 units of pressure, but when the ASTM standardized the test (tentative issue in 1922, standard first formally adopted in 1927), it called for results in units of force.

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 measurement is in pounds-force. In Sweden it is apparently in kilogram-force (kgf), and in Australia, Janka hardness ratings are either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, e.g., “360 janka.”

The hardness of wood usually 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 (radially), 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.

Notes on the table

The pale blue background indicates species growing in North America. Common names are unreliable since two or more species often have the same common name. We show the common name preferred by the Forest Products Laboratory. Except as noted, all samples were tested at 12% moisture content, typical of air-dried wood. Wood varies; a sample picked at random is expected to have a side hardness between about 80% and 120% of the value shown. Blank cells occur where a wood is sold commercially but so far we have found no hardness data.

Side Hardness of Some Woods
Common name Scientific name side hardness,
Janka test,
at 12% moisture content
kilonewtons pounds-force
afrormosia Pericopsis elata 6.9 1560
albarco Cariniana spp. 4.5 1020
alder, red Alnus rubra 2.6 590
alder, white Alnus rhombifolia    
andiroba Carapa guianensis 5.0 1130
angelin Andira inermis 7.8 1750
angelique Dicorynia guianensis 5.7 1290
anime Protium spp.   920
apple Malus sylvestris 7.7 1730
ash, black Fraxinus nigra 3.8 850
ash, blue Fraxinus quadrangulata 9.0 2030
ash, green Fraxinus pennsylvanica 5.3 1200
ash, oregon Fraxinus latifolia 5.2 1160
ash, pumpkin Fraxinus profunda 4.4 990
ash, white Fraxinus americana 5.9 1320
aspen, bigtooth Populus grandidentata 1.9 420
aspen, quaking Populus tremuloides 1.6 350
avodire Turraeanthus africanus 4.8 1080
azobe Lophira alata 14.9 3350
baldcypress Taxcodium distichum 2.3 570
balsa Ochroma pyramidale    
banak Virola spp. 2.3 510
basswood, American Tilia americana 1.8 410
basswood, Carolina Tilia caroliniana    
basswood, white Tilia heterophylla    
beech, American Fagus grandifolia 5.8 1300
benge Guibourtia arnoldiana 7.8 1750
birch, gray Betula populifolia 3.4 760
birch, paper Betula papyrifera 4.0 910
birch, river Betula nigra    
birch, sweet Betula lenta 6.5 1470
birch, yellow Betula alleghaniensis 5.6 1260
boxelder Acer negundo 3.2 720
bubinga Guibourtia spp. 12.0 2690
buckeye, Ohio Aesculus glabra    
buckeye, yellow Aesculus octandra 1.6 350
buckthorn, cascara Rhamnus purshiana 4.6 1040
bulletwood Manilkara bidentata 14.2 3190
butternut Juglans cinerea 2.2 490
buttonwood Conocarpus erectus    
catalpa, northern Catalpa speciosa 2.4 550
catalpa, southern Catalpa bignonioides 2.4 550
cativo Prioria copaifera 2.8 630
cedar, Alaska Chamaecyparis nootkatensis 2.6 580
cedar, atlantic white Chamaecyparis thyoides 1.6 350
cedar, Port Orford Chamaecyparis lawsoniana 3.2 720
cedar, yellow Cupressus nootkatensis 2.6 580
ceiba Ceiba pentandra 1.1 240
chalviande Virola spp.   481
cherry, black Prunus serotina 4.2 950
chestnut, American Castenea dentata 2.4 540
chinkapin, giant Castanopsis chrysophylla 3.2 730
coffeetree, Kentucky Gymnocladus dioicus 6,2 1390
cottonwood) balsam poplar Populus balsamifera 1.3 300
cottonwood, black Populus trichocarpa 1.6 350
cottonwood, eastern Populus deltoides 1.9 430
courbaril Hymenaea courbaril 10.5 2350
cuangare Dialyanthera spp. 1.7 380
cypress, Mexican Cupressus lustianica 2.0 460
degame Calycophyllum candidissimum 8.6 1940
determa Ocotea rubra 2.9 660
dogwood, flowering Cornus florida 9.6 2150
Douglas-fir, coast Pseudotsuga menziesii 3.2 710
Douglas-fir, interior west Pseudotsuga menziesii 2.9 660
Douglas-fir, interior north Pseudotsuga menziesii 2.7 600
Douglas-fir, interior south Pseudotsuga menziesii 2.3 510
ekop Tetraberlinia tubmaniana    
elder, blue Sambucus cerulea 3.7 840
elm, american Ulmus americana 3.7 830
elm, cedar Ulmus crassifolia 5.9 1320
elm, rock Ulmus thomasii 5.9 1320
elm, slippery Ulmus rubra 3.8 860
elm, winged Ulmus alata 6.8 1540
fir, balsam Abies balsamea 1.8 400
fir, California red Abies magnifica 2.2 500
fir, grand Abies grandis 2.2 490
fir, noble Abies procera 1.8 410
fir, pacific silver Abies amabilis 1.9 430
fir, subalpine Abies lasiocarpa 1.6 350
fir, white Abies concolor 2.1 480
goncalo alves Astronium graveolens 9.6 2160
greenheart Chlorocardium rodiei 10.5 2350
hackberry Celtis occidentalis 3.9 880
hackberry, netleaf Celtis reticulata    
(hackberry) sugarberry Celtis laevigata    
hemlock, eastern Tsuga canadensis 2.2 500
hemlock, mountain Tsuga mertensiana 3.0 680
hemlock, western Tsuga heterophylla 2.4 540
hickory, bitternut Carya cordiformis    
hickory, black Carya texana    
hickory, nutmeg Carya myristicaeformis    
hickory, pecan Carya illinoensis 8.1 1820
hickory, sand Carya pallida    
hickory, water Carya aquatica    
hickory. mockernut Carya tomentosa 8.8 1970
hickory, pignut Carya glabra 9.5 2140
hickory, shagbark Carya ovata 8.4 1880
hickory, shellbark Carya lacinosa 8.1 1810
holly, American Ilex opaca 4.5 1020
honeylocust Gleditsia triacanthos 7.0 1580
hophornbeam, eastern Ostrya virginiana 8.3 1860
hornbeam, American Carpinus caroliniana 7.9 1780
hura Hura crepitans 2.4 550
ilomba Pycnanthus angolensis Exell 2.7 610
incense-cedar Libocedrus decurrens 2.1 470
ipe Tabebuia spp., lapacho group 16.4 3680
iroko Chlorophora spp. 5.6 1260
jarrah Eucalyptus marginata 8.5 1910
jelutong Dyera costulata 1.7
(@15%)
390
juniper, alligator Juniperus deppeana 5.2 1160
juniper, western Juniperus occidentalis    
kaneelhart Licaria spp. 12.9 2900
kapur Dryobalanops spp. 5.5 1230
karri Eucalyptus diversicolor 9.1 2040
kempas Koompassia malaccensis 7.6 1710
keruing Dipterocarpus spp. 5.6 1270
larch, western Larix occidentalis 3.7 830
laurel, California Umbellularia californica 5.6 1270
laurel, mountain Kalmia latifolia 8.0 1790
lignumvitae Guaiacum spp. 20.0 4500
limba Terminalia superba 2.2 490
locust, black Robinia pseudoacacia 7.6 1700
macawood Platymiscium spp. 14.0 3150
madrone, Pacific Arbutus menziesii 6.5 1460
(magnolia) cucumber tree Magnolia acuminata 3.1 700
magnolia, southern Magnolia grandiflora 4.5 1020
(magnolia) sweetbay Magnolia virginiana    
mahogany, African Khaya spp. 3.7 830
mahogany, true Swietenia macrophylla 3.6 800
manbarklak Eschweilera spp. 15.5 3480
manni Symphonia globulifera 5.0 1120
maple, bigleaf Acer macrophyllum 3.8 850
maple, black Acer nigrum 5.2 1180
maple, red Acer rubrum 4.2 950
maple, silver Acer saccharimum 3.1 700
maple, sugar Acer saccharum 6.4 1450
marishballi Lincania spp. 15.9 3570
merbau Intsia spp. 6.7 
(@15%)
1500
mersawa Anisoptera spp. 5.7 1290
mesquite Prosopis spp.    
mora Mora spp. 10.2 2300
oak, black Quercus velutina 5.4 1210
oak, cherrybark Quercus falcata var pagodifolia 6.6 1480
oak, southern red Quercus falcata 4.7 1060
oak, laurel Quercus laurifolia 5.4 1210
oak, northern red Quercus rubra 5.7 1290
oak, pin Quercus palustris 6.7 1510
oak, scarlet Quercus coccinea 6.2 1400
oak, shumard Quercus shumardii    
oak, water Quercus nigra 5.3 1190
oak, willow Quercus phellos 6.5 1460
oak, bur Quercus macrocarpa 6.1 1370
oak, chestnut Quercus prinus 5.0 1130
oak, live Quercus virginiana    
oak, overcup Quercus lyrata 5.3 1190
oak, post Quercus stellata 6.0 1360
oak, swamp chestnut Quercus michauxii 5.5 1240
oak, swamp white Quercus bicolor 7.2 1620
oak, white Quercus alba 6.0 1360
obeche Triplochiton scleroxylon 1.9 430
okoume Aucoumea klaineana 1.7 380
opepe Nauclea diderrichii 7.3 1630
osage orange Maclura pomifera 9.1
(green)
2040
(green)
ovangkol Guibourtia ehie    
para-angelim Hymenolobium excelsum 7.7 1720
parana-pine Araucaria augustifolia 3.5 780
pau marfim Balfourodendron riedelianum    
peroba de campos Paratecoma peroba 7.1 1600
peroba rosa Aspidosperma spp., peroba group 7.7 1730
persimmon, common Diospyros virginiana 10.2 2300
pilon Hyeronima spp. 7.6 1700
pine, Caribbean Pinus caribaea 5.5 1240
pine, eastern white Pinus strobus 1.7 380
pine, jack Pinus banksiana 2.5 570
pine, Jeffrey Pinus jeffreyi 2.2 500
pine, limber Pinus flexilis 1.9 430
pine, loblolly Pinus taeda 3.1 690
pine, lodgepole Pinus contorta 2.1 480
pine, longleaf Pinus palustris 3.9 870
pine, ocote Pinus oocarpa 4.0 910
pine, pinyon Pinus edulis 3.8 860
pine, pitch Pinus rigida 2.8 620
pine, pond Pinus serotina 3.3 740
pine, ponderosa Pinus ponderosa 2.0 460
pine, Monterey Pinus radiata 3.3 750*
pine. red Pinus resinosa 2.5 560
pine, sand Pinus clausa 3.3 730
pine, shortleaf Pinus echinata 3.1 690
pine, slash Pinus elliotti    
pine, spruce Pinus glabra 2.9 660
pine, sugar Pinus lambertiana 1.7 380
pine, Table Mountain Pinus pungens 2.9 660
pine, virginia Pinus virginiana 3.3 740
pine, western white Pinus monticola 1.9 420
piquia Caryocar spp. 7.7 1720
primavera Tabebula donnell-smithii 2.9 660
pulgande Dacryodes spp.   666
purpleheart Peltogyne spp. 8.3 1860
ramin Gonystylus bancanus 5.8 1300
redcedar, eastern  Juniperus virginiana 4.0 900
redcedar, southern Juniperus silicicola 2.7 610
redcedar, western  Thuja plicata  1.6 350
redwood, old growth Sequoia sempervirens 2.1 480
redwood, second growth Sequoia sempervirens 1.9 420
robe Tabebul spp., roble group 4.3 960
rosewood, Brazilian Dalbergia nigra 12.1 2720
rosewood, Indian Dalbergia latifolia 14.1 3170
sajo Campnosperma panamensis   425
sande Brosimum spp., utile group 4.0 900
santa maria Calophyllum brasiliense 5.1 1150
sapele Entandrophragma cylindricum 6.7 1510
sassafras Sassafras albidum 2.8 630
sepetir Pseudosindora palustris 6.3 1410
serviceberry Amelanchier spp. 8.0 1800
shorea Shorea spp., baulau group 7.9 1780
(shorea) dark red meranti Shorea spp., lauan-meranti group 3.5 780
(shorea) light red meranti Shorea spp., lauan-meranti group 2.0 460
(shorea) white meranti Shorea spp., lauan-meranti group 5.1
(@15%)
1140
(shorea) yellow meranti Shorea spp., lauan-meranti group 3.4 770
silverbell, Carolina Halesia carolina 2.6 590
sourwood Oxydendrum arboreum 4.2 940
Spanish-cedar Cedrela spp. 2.7 600
spruce, black Picea mariana 2.3 520
spruce, Engelmann Picea engelmanni 1.7 390
spruce, red Picea rubra 2.2 490
spruce, Sitka Picea sitchensis 2.3 510
spruce, white Picea glauca 2.1 480
sucupira Bowdichia spp.    
sucupira Diplotropis purpurea 9.5 2140
sumac, staghorn Rhus typhina 3.0 680
sweetgum Liquidambar styraciflua 3.8 850
sycamore, american Platanus occidentalis 3.4 770
tamarack Larix laricina 2.6 590
tanoak Lithocarpus densiflorus    
teak Tectona grandis 4.4 1000
tornillo Cedrelinga cateniformis   870
(green)
tree-of-heaven Ailanthus altissima 7.7 1731
tulapueta Osteophloeum platyspermum   512
tupelo, black Nyssa sylvatica 3.6 810
tupelo. water Nyssa aquatica 3.9 880
wallaba Eperua spp. 9.1 2040
walnut, black Juglans nigra 4.5 1010
white-cedar, northern  Thuja occidentalis 1.4 320
willow, black Salix nigra    
witch hazel Hamamelis virginica 6.8 1530
yellow poplar Liriodendron tulipifera 2.4 540
yew. Pacific Taxus brevifolia 7.1 1600

*Authorities differ significantly on the hardness of Pinus radiata, with published values as high as 792 lbs-force (3.5 kilonewtons) and as low as 625 lbf (2.8 kN).

sources

Forest Products Laboratory.
Wood Handbook: Wood as an Engineering Material.
Technical Report FPL-GTR-113.
Madison, WI: U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1999.

Downloadable from www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf  See also the 2010 edition, which is downloadable chapter by chapter. Hardness information is in chapter 5.

Harry A. Alden
Hardwoods of North America.
General Technical Report FPL-GTR-83.
Madison, WI: U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1995.

Downloadable from www.fpl.fs.fed.us/publications/fplgtr83.pdf

Harry A. Alden
Softwoods of North America.
General Technical Report FPL-GTR-102.
Madison, WI: U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1997.

Downloadable from www.fpl.fs.fed.us/publications/fplgtr102.pdf

B. Alan Bendtsen and Martin Chudnoff.
Properties of Seven Columbian Woods.
USDA, Forest Service, Forest Products Laboratory Research Note FPL-0242
Madison, WI: Forest Products Lab, January 1981.

Martin Chudnoff.
Tropical Timbers of the World.
Agriculture Handbook 607.
Madison, WI: U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 1979.

Downloadable from www.fpl.fs.fed.us/publications/chud_total.pdf

David W. Green, Marshall Begel and William Nelson.
Janka Hardness Using Nonstandard Specimens.
Research Note FPL-RN-0303.
Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 2006.

Wayne C. Lewis.
Hardness Modulus as an Alternate Measure of Hardness to the Standard Janka Ball for Wood and Wood-Base Materials.
USDA, Forest Service, Forest Products Laboratory Research Note FPL-0189
Madison, WI: Forest Products Laboratory, March 1968.

Michael C. Wiemann and David W. Green.
Estimating Janka Hardness from Specific Gravity for Tropical and Temperate Species.
USDA, Forest Service, Forest Products Laboratory Research Paper FPL-RP-643
Madison, WI: Forest Products Laboratory, September 2007.

Downloadable from www.fpl.fs.fed.us/documnts/fplrn/fpl_rn303.pdf

resources

Standards:
ASTM D1037-99. Standard Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials.
ASTM D143-94(2000)e1 Standard Methods of Testing Small Clear Specimens of Timber.
ISO 3350:1975. Wood–Determination of static hardness.
ISO 3351:1975. Wood–Determination of resistance to impact indentation.

Janka hardness ratings can also be found at sites selling flooring, such as:

www.wflooring.com/Technical_Info/Species_Tech_Info/species_hardness.htm

www.zoltanfloors.com/tech.html

Some information sources say or imply, incorrectly, that Janka hardness is measured in units of pressure, such as pounds per square inch, and that side hardness is a synonym for Janka hardness.

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