Hardness Scale

The Janka Hardness Scale: What It Is and Why It Matters

If you've ever dragged a piece of furniture across a hardwood floor and held your breath, you already understand hardness. The Janka scale just puts a number on it.

The test itself is beautifully simple. You take a steel ball, 0.444 inches in diameter (about the size of a large marble), and you press it into a piece of wood until it's embedded halfway. The amount of force it takes to get there, measured in pounds-force (lbf), is the Janka hardness rating for that species.

The test was developed in 1906 by an Austrian-born researcher named Gabriel Janka, who was working at the time for the U.S. Department of Agriculture's Forest Products Laboratory. The problem he was trying to solve was practical: the lumber industry needed a reliable, repeatable way to compare how different species held up under wear. Flooring manufacturers needed it. Furniture builders needed it. The military needed it for everything from rifle stocks to ship decking.

Over a century later, the test hasn't changed much. It's still the standard. And for good reason. It gives you a single number that tells you a lot about how a species will perform in the real world.

What the Numbers Actually Tell You

A low Janka rating (under 1000 lbf) means the wood is softer. It'll dent more easily, but it's also generally easier to work with hand tools, takes stain well, and can have a warmth to it that harder woods sometimes lack. Cherry at 950 and walnut at 1010 live in this range. They're not fragile by any means, but you'll want to think about where and how you're using them.

Mid-range (1000 to 1500 lbf) is where most popular furniture and cabinet woods land. White oak at 1360 is the classic example. Hard enough to take a beating, workable enough that your tools don't hate you for it.

High Janka ratings (1500 and above) mean serious density. Hickory at 1820 is about as hard as domestic hardwoods get. These species are the go-to for flooring, heavy-use surfaces, and anything that needs to stand up to years of abuse without showing it.

A Few Things the Janka Scale Doesn't Tell You

Hardness isn't the whole story. A species can be hard but brittle. Or soft but incredibly tough and flexible. Janka doesn't measure how well wood resists splitting, how it responds to moisture changes, or how it takes a finish. It's one important data point, not the only one.

That's why we include workability notes and common uses in our species guide below. The Janka number gets you started. The rest helps you pick the right wood for what you're actually building.