Janka Scale for Common Woods (Spec Guide)

The Janka test compares how much force it takes to dent wood with a steel ball. Higher values usually mean better resistance to small, localized dents, but they do not predict every kind of wear or prove that a wood is right for your project. Use the rating with species, grade, moisture, finish, and intended use.

A wood’s Janka number can look like a simple durability score. That is where buyers can get misled: a high rating does not guarantee scratch-proof floors, long-lasting finish, or a board that is easy to install. The useful question is narrower: how well is this wood likely to resist a small indentation under conditions comparable to the test?

I use Janka values as a first comparison, not a final verdict. Below, you’ll find common published ratings, how to read them, and a practical way to match a species to flooring, furniture, trim, or a work surface.

Wood Hardness Selection and Project Safety

Janka hardness is a comparative measure of a wood’s resistance to a specific kind of dent. It can help narrow a species list, but it is not a full measure of durability. Start by defining the project’s use, then consider the rating alongside finish, board construction, moisture, and installation needs.

What the test measures

The Janka test measures the force needed to press a steel ball 0.444 inches (11.28 mm) wide into wood until half the ball’s diameter is embedded. ASTM D143 describes procedures for testing wood properties, including hardness. Results are commonly listed in pounds-force (lbf).

A higher number generally means greater resistance to that localized indentation when the tested materials and conditions are comparable. It does not directly measure scratch resistance, abrasion, bending strength, impact performance, or resistance to rot and weather. Those are different properties, and a finish can affect surface wear without changing the wood’s Janka rating.

How to use a rating

Treat the value as one useful specification, not a universal durability rank. For a floor, consider expected foot traffic, grit, footwear, furniture movement, finish, board construction, and maintenance. For a work surface, think about the tools and objects that may strike or press into it. Trim and furniture may face far less impact than a busy floor.

Very hard wood can also take more effort to cut and fasten. A high score alone is not a reason to choose a species if the project’s appearance, cost, maintenance, or installation requirements point elsewhere. The best choice meets the actual service conditions without asking the rating to answer questions it was not designed to answer.

Safety when working dense wood

Dense wood can split, burn during cutting, or bind against unsuitable tooling. If a cut starts to burn or the tool binds, stop rather than forcing it. Isolate power before making adjustments, secure the workpiece, use sharp and compatible tooling, and follow the tool maker’s guarding and operating instructions.

Species Ratings and Application Fit

Published Janka ratings give a practical way to compare familiar woods, but the numbers are not exact constants for every board. Species identification, growing conditions, sample preparation, moisture, and test method can all affect a result. Confirm the supplier’s stated species and test basis before using a number to specify a purchase.

These are approximate common published values, not guaranteed values for every shipment. Many published figures are reported near 12% moisture content, but sources and test conditions can differ. Ask the supplier what species the product is, whether the figure is for that exact species, and what moisture and test basis applies.

Compare the number with the job

For flooring in a busy area, a higher Janka value may help reduce dents from localized pressure, but it does not prevent scratches from grit or protect a worn finish. A lower-rated species may still suit a room with light use, proper floor protection, and an appropriate finish. Hardness should guide the comparison, not settle it.

For furniture and trim, appearance, machining, stability, joinery, and finish may matter as much as dent resistance. For a work surface, consider the kinds of impacts and cuts expected; Janka does not describe resistance to a knife edge or every tool mark. Match the species and grade to the use rather than choosing the largest number in the table.

Three project-planning examples

These are selection scenarios, not claims about a specific installed product.

• A busy household floor: Compare northern red oak, hard maple, hickory, and other suitable options by rating, then consider finish, board construction, traffic, and upkeep. A higher rating can be one point in favor, but does not remove the need to control grit or protect the finish.
• A furniture piece with visible grain: Compare species for the look and finish you want, then check that the hardness fits likely knocks and daily use. Black walnut and black cherry are close in the table, so the rating alone may not distinguish them for a design choice.
• A trim project: If the trim will see little impact, do not assume the highest-rated wood is automatically best. Fit, finish, appearance, availability, and how the material will be fastened may be more useful deciding factors.

Cutting, Fastening, and Installation Practices

Good installation starts with knowing what material you have and what the manufacturer requires. Janka ratings do not specify saw, motor, blade, or chain compatibility. Confirm species, grade, construction, and moisture condition, then test your tooling and fasteners on offcuts before working on visible or finished pieces.

1. Define service conditions

Write down where the material will be used and what it will face: indoor or outdoor exposure, foot traffic, impacts, moisture, appearance goals, and acceptable maintenance. Janka hardness is not an outdoor-durability rating. Do not use it as a substitute for checking the product’s intended environment and care instructions.

2. Verify the material

Confirm the botanical species and grade with the supplier. Check whether the product is solid wood or engineered construction, and request the documented Janka value and its test basis. For flooring, inspect boards for defects and follow the manufacturer’s instructions for acclimating the product to project conditions.

Species names can be broad or used inconsistently in sales listings. If the number will affect a purchase or specification, ask for the exact species rather than relying on a general label such as “maple” or “pine.” Confirm that the rating refers to the named species and not a related wood.

3. Test cuts and fasteners

Use sharp, species-appropriate tooling and follow its manufacturer’s limits. Make a test cut on scrap from the same material when possible. Test fasteners on an offcut as well; predrill near board ends or wherever the wood is likely to split, and follow the flooring, fastener, and tool instructions.

Dense wood can demand careful feed and secure setup. Do not force a dull or unsuitable blade through it. Binding can damage the work and create a kickback hazard. Stop, isolate power before changing the setup, and check the tool, blade, and workpiece before continuing.

4. Inspect as you work

Look for dents, splits, loose fasteners, damaged edges, and finish defects. A high Janka rating cannot prevent a board from splitting under a poorly placed fastener or a damaged finish from showing wear. Address problems before they become hidden under trim or another layer of work.

Finish Care, Inspection, and Material Storage

A Janka rating describes the wood’s response to a specific indentation test; it does not rate the finish or predict all surface wear. Protect the completed material in ways suited to its use, inspect it for damage, and follow the product maker’s care instructions. Storage and moisture control also matter before installation.

Protect the surface

Use the finish specified for the product and maintain it according to the maker’s instructions. On floors, grit can scratch a finish, so routine cleaning and suitable entry mats can help limit what gets tracked inside. Furniture pads can reduce direct contact between heavy items and a floor, but they do not change the wood’s Janka value.

When a surface gets damaged, assess the finish and wood separately. A scratch may be in the coating, in the wood, or both. Hardness alone will not tell you how easy a particular finish is to repair or how often it needs care.

Store and inspect material

Keep material in the conditions and manner required by its supplier. For flooring, use the maker’s guidance on acclimation rather than relying on a fixed number of days. Check boards before installation, and investigate moisture concerns with a suitable meter and the product instructions. A Janka rating is not a moisture specification.

As a final check, keep the key details together: species, grade, solid or engineered construction, reported Janka value, moisture information, finish, and installation requirements. That record makes it easier to compare products accurately and revisit care guidance later.

Conclusion: Janka is most useful as a clear, limited comparison of dent resistance. Choose a species for its actual service conditions, verify the product behind the rating, and plan for its finish and installation. A larger number can inform your choice, but it cannot replace those checks.

Frequently asked questions

What does a Janka rating measure?
It measures the force needed to embed a specified steel ball halfway into wood. It compares resistance to localized indentation under test conditions.

What does a higher Janka number mean?
It generally indicates greater resistance to localized denting in a comparable test. It does not prove greater scratch resistance, structural strength, or outdoor durability.

What is the Janka rating for red oak?
Northern red oak is commonly listed at about 1,290 lbf. Published values can vary, so confirm the test basis and species with the supplier.

Is hard maple harder than northern red oak?
In the approximate values in this guide, hard maple is 1,450 lbf and northern red oak is 1,290 lbf. The figures are useful for comparison, not exact guarantees for every board.

Does Janka predict scratches on a wood floor?
No. Janka measures resistance to a particular indentation, not surface scratching or abrasion. Finish, grit, footwear, and care also affect how a floor looks over time.

Are Janka ratings reported at a set moisture content?
Many published values are reported near 12% moisture content, but sources and test conditions vary. Ask the supplier for the moisture condition and method behind its figure.

Can I use Janka to choose wood for outdoor use?
Not by itself. The rating does not measure rot resistance or weather durability. Confirm that the species and product are intended for the outdoor conditions in your project.

Does a high Janka rating mean wood is harder to install?
It can signal that careful, sharp tooling and suitable fasteners matter, but the rating does not specify tool compatibility. Test cuts and fasteners on offcuts and follow manufacturer instructions.

Should I always choose the highest-rated wood for flooring?
No. Compare dent resistance with traffic, finish, board construction, appearance, maintenance, and installation requirements. Choose the material that fits the whole project.

How do I verify the Janka rating before buying?
Ask for the exact botanical species, product construction, documented value, and test basis. Check that the rating refers to the species being sold rather than a broad or unclear trade name.

(This article was written by one of our staff writers, Samuel Vance. Visit our Meet the Team page.)