What the number means
Janka side hardness is the load needed to press a steel ball 0.444 in (11.28 mm) across into the side of a board to half its diameter. The result is a force, given here in pounds-force (lbf) with newtons (N) alongside. A higher number means the wood resists dents and wear better.
Reading the table
- Dry (12%) and green. Dry values are for wood at 12% moisture content, close to furniture in a heated house; green values are for freshly cut wood and are lower. Compare dry with dry.
- US and imported. The two sources were tested differently: US species by the Forest Products Laboratory to one standard, imported species by many laboratories, then adjusted. The filter keeps them apart if you want like-for-like.
- Names. Species follow the handbook’s names. Imported species carry the scientific name the handbook gives; US species are listed by common name, as the handbook lists them.
- Group names. “Red oak” and “white oak” are each a group of species, and their hardness varies; the table gives each species the handbook tests.
| Species | Dry hardness (lbf) | Relative to eastern white pine |
|---|---|---|
| Eastern white pine | 380 | 1× |
| Black cherry | 950 | 2.5× |
| Northern red oak | 1,290 | 3.4× |
| Sugar maple | 1,450 | 3.8× |
| Shagbark hickory | 1,880 | 4.9× |
Sugar maple takes nearly four times the load of eastern white pine to dent the same amount, which is why it is used for workbench tops and floors. Red oak and white oak (1,360 lbf) are close enough that hardness alone will not decide between them.
Limits of a hardness figure
- Wood varies. Each value is an average for small, clear, straight-grained samples. Boards of the same species differ with growth rate, density and moisture, often by more than the gap between neighbouring species in the table.
- Hardness is not strength or durability. It predicts resistance to denting and wear, and roughly how hard a wood is to cut and nail. It says nothing about stiffness, rot resistance or stability.
- Other charts may differ. Figures elsewhere may come from other tests, other moisture contents or end-grain hardness. Check the source before comparing numbers between charts.
Harder woods are harder on edges too: a chisel or plane iron dulls faster in hickory than in pine, and dense species split more readily around a screw driven without a pilot hole. Bit diameters in every series are on the drill bit size chart. For how species work and move, see the wood species pages.
Sources
Every value is copied from the handbook’s tables; where a table leaves a cell blank, the chart leaves it blank. US values are from the Forest Products Laboratory’s own tests; imported values come from other laboratories’ published tests, adjusted by the handbook to 12% moisture content (a few at 15%, marked). The handbook gives the true hickories’ hardness from Bendtsen and Ethington (1975). Newtons are converted at 1 lbf = 4.448 N and rounded to the nearest 10.
- 1.
Christopher Adam Senalik and Benjamin Farber. Chapter 5: Mechanical Properties of Wood. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Side hardness of US species from FPL tests by ASTM D143 (Table 5–3b) and of imported species compiled from world literature (Table 5–5b), green and dry; the definition of the Janka test.
About this chart
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