The Janka hardness test measures the force required to embed a 0.444-inch steel ball halfway into wood. This standardized test provides comparable hardness ratings across wood species, helping you predict durability, workability, and appropriate applications.
How the Test Works
A steel ball 0.444 inches in diameter (11.28mm) is pressed into the wood surface until exactly half the ball’s diameter penetrates—0.222 inches. The force required for this penetration, measured in pounds-force (lbf), is the Janka rating. Higher numbers indicate harder wood requiring more force to dent.
The test measures hardness perpendicular to the grain—the side grain of a board. Wood is significantly harder on end grain and slightly softer on face grain, but side grain ratings provide the standard comparison point.
Common Softwoods
Eastern white pine rates 380 lbf—one of the softest commercial woods. It dents easily from impacts and doesn’t hold fasteners well in thin sections. The softness makes it easy to work but limits applications to low-wear situations.
Douglas fir rates 660 lbf—harder than pine but still in the softwood range. The increased density provides better nail-holding and wear resistance while remaining reasonably easy to work with hand and power tools.
Southern yellow pine rates 690-870 lbf depending on the specific variety. The wide growth rings create density variations within boards, leading to inconsistent working properties. The hardest yellow pine approaches some hardwoods in durability.
Entry-Level Hardwoods
Poplar rates 540 lbf—technically a hardwood but softer than many softwoods. It works easily and finishes well, making it popular for painted furniture and secondary wood applications. The softness limits its use for high-wear surfaces.
Red alder rates 590 lbf—similar to poplar in softness despite being a hardwood. It’s used extensively in cabinets and furniture where the hardwood appearance matters more than extreme durability.
Basswood rates 410 lbf—very soft for a hardwood. It’s prized for carving due to easy cutting but unsuitable for structural applications or high-wear surfaces.
Mid-Range Hardwoods
Cherry rates 950 lbf—moderately hard with good machining properties. It provides adequate durability for furniture while remaining pleasant to work with hand tools. The moderate hardness balances workability and performance.
Walnut rates 1,010 lbf—slightly harder than cherry with excellent working properties. It holds details well in carving and resists denting better than softer hardwoods. The density is high enough for furniture but not so high that it’s difficult to machine.
Birch (yellow) rates 1,260 lbf—significantly harder than cherry or walnut. It provides good wear resistance for cabinets and furniture. The increased hardness makes it noticeably harder to work than softer species, requiring sharp tools and more power.
Hard Domestic Species
Red oak rates 1,290 lbf—the benchmark hardwood for flooring and furniture. Its hardness provides good wear resistance while remaining machinable with standard woodworking tools. The open grain is distinctive but also collects dirt in high-wear applications.
White oak rates 1,360 lbf—slightly harder than red oak with tighter grain. The increased density improves water resistance and wear characteristics. It’s preferred for outdoor applications and situations requiring maximum durability.
Hard maple rates 1,450 lbf—one of the hardest domestic woods. It provides excellent wear resistance for cutting boards, work surfaces, and flooring. The hardness means dull tools won’t cut it effectively—sharp edges are essential.
Very Hard Species
Hickory rates 1,820 lbf—extremely hard with excellent shock resistance. It’s used for tool handles, flooring, and applications requiring maximum impact resistance. The hardness makes it challenging to work, requiring patience and very sharp tools.
Mesquite rates 2,345 lbf—very hard southwestern species used for specialty applications. It’s difficult to machine and wears tools quickly but provides extreme durability where needed.
Tropical Hardwoods
Teak rates 1,155 lbf—moderately hard but highly prized for its natural oils providing water and rot resistance. The rating doesn’t reflect its outdoor durability, which exceeds much harder woods lacking natural preservatives.
Mahogany (genuine) rates 800-900 lbf depending on variety—softer than domestic hardwoods but valued for stability and workability. The lower hardness makes it easy to machine to fine tolerances.
Ipe rates 3,680 lbf—extremely hard Brazilian wood used for decking. It’s so hard that it dulls carbide tooling quickly and requires pre-drilling for fasteners. The extreme hardness provides decades of outdoor durability.
Practical Implications
Woods below 700 lbf dent easily and show wear quickly on work surfaces. Use them for painted projects, low-wear furniture, and applications where hardness doesn’t matter.
Woods from 700-1,200 lbf handle moderate wear adequately. They work well for furniture, cabinets, and interior trim. Machining remains reasonably easy with sharp tools.
Woods from 1,200-1,600 lbf provide good wear resistance for flooring, cutting boards, and high-use furniture. They require sharp tools and more powerful machines but deliver excellent durability.
Woods above 1,600 lbf are specialty applications. They’re challenging to machine and may not be necessary unless extreme durability is required. The working difficulty often isn’t worth the extra hardness unless you specifically need maximum wear resistance.
Tool Wear Correlation
Hardness directly affects tool life. Planing maple (1,450 lbf) dulls edges approximately three times faster than cherry (950 lbf). Router bits and saw blades wear similarly—harder woods demand more frequent sharpening and tool replacement.
Woods above 1,500 lbf may require carbide tooling for economical machining. High-speed steel tools dull too quickly to be practical except for small projects. Factor tool wear into project costs when working with very hard species.
Flooring Selection
For residential flooring, minimum hardness of 1,000 lbf provides adequate durability. Woods below this rating show denting and wear in high-traffic areas within a few years.
For commercial flooring or homes with large dogs, choose woods above 1,200 lbf. The increased hardness prevents most denting from normal use and extends refinishing intervals.
Hardness vs Other Properties
Hardness doesn’t predict all wood characteristics. Teak’s moderate rating doesn’t reflect its exceptional outdoor durability. Balsa is extremely soft but has high strength-to-weight ratio. Hardness is one factor among many—consider grain structure, stability, workability, and appearance alongside the Janka rating when selecting wood species.
