Janka hardness explained

The Janka hardness rating is the force needed to embed an 11.28 mm (0.444 inch) steel ball into wood to half the ball's diameter. The Wood Handbook defines hardness as resistance to indentation measured with a modified Janka test, using exactly that ball and depth¹. A higher number means a wood resists denting better. This page explains the test, the units, the difference between side and end hardness, the limits, and the Brinell method used in Europe. For ratings by species, see our hardness chart.

What does the Janka test measure?

The Wood Handbook defines the load as the force "required to embed" the ball to one-half its diameter¹. The Wood Database gives the same ball, a 0.444 inch (11.28 mm) diameter steel ball driven to half its diameter, and says values are for wood dried to 12% moisture content unless noted⁴. It describes the number as an indicator of how well a wood withstands dents, dings and wear, and indirectly of how hard it is to nail, screw, sand or saw⁴.

The method has a long history. The Forest Products Laboratory's Research Note says Janka proposed a modified Brinell hardness test for wood in 1906, based on the force needed to embed a 0.444 inch steel hemisphere, a circle with a projected area of 100 mm²². The test became ASTM D143 in 1927, and the D143 value has always been specified as the load at a penetration of 0.222 inch (half the ball's diameter)². The standard specimen is 2 by 2 inches in cross-section and 6 inches long².

What are the units, lbf and newtons?

Janka values are given in pounds-force (lbf) or newtons (N)⁴. The Wood Handbook prints both, with the metric table "converted to metric units directly" from the inch-pound table¹.

The two sources round their newton figures differently, so small differences in N values are not meaningful. When comparing floors, use one source and one unit throughout.

What is side hardness and end hardness?

FPL's Research Note says the standard test distinguishes between hardness on the end and on the side of the piece, with no distinction between radial and tangential faces². For side hardness, the standard calls for two indentations on the tangential face and two on the radial face, and the average of the four loads is reported as side hardness². The Wood Handbook defines side hardness as hardness measured when load is perpendicular to the grain¹. Analysis of historical data found no difference between radial and tangential side hardness².

Most species tables, including the Wood Handbook's, list side hardness. FPL's hardness research was prompted by growing interest in tropical species for flooring, and notes that the Wood Handbook gives Janka side hardness values for most domestic species and almost 80 imported ones³. For engineered wood and other board floors, side hardness is therefore the figure you will normally find. End-grain flooring is different, because ISO's vocabulary describes wood block paving as blocks installed so that an end grain surface serves as a wear area⁸. The sources opened here do not publish end-hardness values, so the Janka numbers in a species table should not be assumed to apply directly to an end-grain floor.

What affects a Janka number?

• Moisture. FPL's analysis of mean values for 237 hardwood and 47 softwood species concluded that dry wood is harder than green wood, by about 31% for temperate hardwoods, 43% for temperate softwoods and 26% for tropical hardwoods³. That is why tables state a moisture content, usually 12%⁴.
• Density. FPL developed regression equations that predict side hardness from specific gravity; hardness and specific gravity have the same relationship in temperate and tropical hardwoods, but softwoods follow a different one³. The Wood Database notes some of its values are estimated from specific gravity rather than measured⁴.
• Anatomical direction. A 2020 study notes hardness depends on anatomical direction and can vary by up to 50% within the same species⁵.
• Specimen scatter. FPL's published side hardness observations on standard specimens had a coefficient of variation averaging about 22%².

What are the limits of the Janka scale?

The Wood Database describes hardness as an indicator rather than a complete performance measure and says shock resistance is also important⁴. Sydor et al. add that measuring the diameter of an indentation in wood is subjective, since the border is not clear, and that depth-based measurements are more unambiguous⁵. The Wood Handbook defines the property as resistance to indentation¹. NWFA tells installers that Janka ratings give only an idea of approximately how each species can be affected by indentation forces such as high heels, dog claws and heavy furniture⁹.

What is Brinell hardness and EN 1534?

In Europe, flooring is more often tested by a Brinell-type test. Brinell hardness presses a steel or carbide ball into the sample, removes it, and measures the diameter of the permanent dent with a microscope⁵. Janka and Brinell are described as the two most popular methods for wood, and a comparison cited by Sydor et al. concluded that the Brinell test gave the most reliable results for flooring materials⁵. Janka's own method, as noted, began as a modified Brinell test².

The European standard is EN 1534. The 2020 edition, "Wood flooring and parquet. Determination of resistance to indentation. Test method", is listed by BSI as current from 31 January 2020 and specifies a method for determining the resistance to indentation of wood flooring⁶. The 2000 edition's title, as listed by AFNOR, named the Brinell test directly, and its abstract refers to the Brinell test⁷. Sydor et al. describe EN 1534's loading as 1 kN reached in 15 ± 3 seconds, held for 25 ± 5 seconds and fully released⁵. Our flooring standards guide lists the full EN suite.

A practical point follows: a Brinell figure and a Janka figure are on different scales. The sources opened here give no conversion, so compare like with like, and ask a maker which test its figure came from.

How do finish and construction affect dent resistance?

The finish question is contested. NWFA says surface finishes minimally influence the effects of indentation forces⁹. The Wood Handbook says smooth film finishes, especially thicker ones, can also protect wood from scratches and dents, and that thicker, harder films are needed for high-wear uses such as floors¹. Both can be true if protection against scratches differs from resistance to a heavy point load. See wood floor finishes.

For construction, NWFA says an engineered floor's appearance is set by its wear layer, which is the species chosen⁹. Whether core layers change how the surface dents is not quantified in the sources opened, so the Janka value for an engineered floor tells you about the wear-layer species, not the whole board. Species pages such as hard maple, hickory and European oak give each rating with its source, and the hardness chart lines them up.

Hardness also feeds one wood-specific usage class scheme: France's parquet standard crosses a Brinell hardness class with wear-layer thickness, as explained in usage classes 21 to 34.

This page compiles published data from the sources listed above. Read our editorial policy. Last updated 3 Nov 2026.