Understanding the Janka Hardness Test

The Janka hardness test is a method for evaluating wood’s resistance to denting and wear. The test measures the force required to press an 11.28-millimeter (7⁄16-inch) steel ball halfway into a wood sample. This diameter was specifically chosen to create an indentation area of 100 square millimeters (1 cm²) for standardized comparison.  The Janka hardness test was developed by Austrian-American researcher Gabriel Janka (1864–1932)

A primary use of Janka ratings is determining a wood species’ suitability for flooring. For hardwood flooring, samples typically measure 80 mm × 150 mm (3 in × 6 in) and are tested under ASTM D1037 standards. When assessing lumber, the test is conducted on heartwood (trunk wood) at 12% moisture content, free of knots.  While the Janka scale helps compare wood hardness, it’s not an absolute predictor of wood flooring durability.

What Does All This Mean When Buying Custom Furniture?

By using the Janka scale as a reference, you can make an informed decision and select wood species that align with your lifestyle and furniture needs. For example, if you have kids who use the kitchen table to build Legos and play with action figures while you cook dinner, soft pine will likely dent under those conditions, whereas walnut might be a better choice.

That said, my role as a custom furniture designer is to help you find the right balance between style, functionality, and durability when designing your furniture. Life often requires compromises, while the most durable wood available may not match your aesthetic preferences, I’m here to guide you toward the best wood species for your specific needs.

Janka Hardness Chart

Note: Not all species of wood listed below are available to build furniture out of.  Some species may be endangered or not harvested in quantities sufficient for the furniture industry.