This number is incredibly useful in directly determining how well a wood will withstand dents, dings, and wear—as well as indirectly predicting the difficulty in nailing, screwing, sanding, or sawing a given wood species.

Janka hardness testing
Janka hardness testing

The actual number listed in the wood profile is the amount of pounds-force (lbf) or newtons (N) required to imbed a .444″ (11.28 mm) diameter steel ball into the wood to half the ball’s diameter. This number is given for wood that has been dried to a 12% moisture content, unless otherwise noted.

For reference, white oak has a Janka hardness of 1,350 lbf (5,990 N), while the super-hard lignum vitae has a hardness of an astounding 4,390 lbf (19,510 N). (Who could imagine a wood species that is over three times harder than white oak?) On the lower end of the spectrum, basswood has a hardness of around 410 lbf (1,820 N).

hardness

Also, in some instances (where noted), I’ve estimated the Janka hardness value using equations that use the wood’s basic specific gravity, as found in the paper, “Estimating Janka Hardness from Specific Gravity for Tropical and Temperate Species.”

Related Articles:

Are you an aspiring wood nerd?

The poster, Worldwide Woods, Ranked by Hardness, should be required reading for anyone enrolled in the school of wood nerdery. I have amassed over 500 wood species on a single poster, arranged into eight major geographic regions, with each wood sorted and ranked according to its Janka hardness. Each wood has been meticulously documented and photographed, listed with its Janka hardness value (in lbf) and geographic and global hardness rankings. Consider this: the venerable Red Oak (Quercus rubra) sits at only #33 in North America and #278 worldwide for hardness! Aspiring wood nerds be advised: your syllabus may be calling for Worldwide Woods as part of your next assignment!

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Keith GebhardtMarciPine GuyRamon AlvarezAntony Croft Recent comment authors
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Keith Gebhardt
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Keith Gebhardt

I sent you an email, but here is the short version. I wonder if you could test ginkgo biloba for its janka rating. At almost 270 million years old, I’m surprised it’s not listed anywhere. There is no tree that has stood through glacier shifts, continental shifts, ice ages, dinosaurs, and even mankind. Definitely a worthy wood to be catalogued.

Marci
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Marci

I was wondering your thoughts on a butcher block counter. Where would you draw the line for the hardness? (Nobody likes dings and dents all over their counters) Also, when will this become available again?

Pine Guy
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Pine Guy

So, this would measure the ability of a wood be bulletproof?

Ramon Alvarez
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Ramon Alvarez

What size pieces are needed to run a Janka test and where can these tests be carried out?

Muzzled ?????? ?????????
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Muzzled ?????? ?????????

We are install solid wood/sand poly floor in a new home with a full basement, what vapor barrier should we use

stephensaugnier
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stephensaugnier

I had a question – At what measure of hardness is a wood classified as a hardwood or softwood? Is there a specific threshold?