To determine how hard a certain type (species) of wood is, the industry has developed a scale called Janka. A small steel ball is pushed into a sample of the wood up to half its height, and the force needed to do so is measured. The harder the wood, the higher the rating. It helps to determine how long a piece of furniture or flooring will last; how well it will be able to withstand everyday use.
The units of the measurement can cause confusion: in America, pounds-force (lbs) is used, while in Europe and Australia, kilogram-force (kgf) or Newton (N) is more usual. In the tables below, we note both lbs and N.
First we list wood species that are very hard (usually above 1,000 lbs) – but as you can see, their hardness varies significantly in this category.
| Species | Janka (lbs) | Janka (N) |
| Ebony (Brazilian) | 3,700 | 16,000 |
| Brazilian walnut | 3,680 | 16,400 |
| Ebony | 3,200 | 14,300 |
| Bamboo | 3,000 | 13,000 |
| Red mahogany | 2,700 | 12,000 |
| Golden teak | 2,300 | 10,400 |
| Tigerwood | 1,900 | 8,200 |
| Satinwood | 1,800 | 8,100 |
| Rosewood | 1,800 | 8,100 |
| Highland beech | 1,700 | 7,500 |
| Maple | 1,450 | 6,400 |
| White oak | 1,400 | 6,000 |
| Ash | 1,300 | 5,900 |
| Teak, English oak | 1,100 | 5,000 |
| Black walnut | 1,000 | 4,500 |
Between 500 and 1,000 lbs, wood is usually classified as hard or suitable for hard. These are easier to work with, but still reasonably resilient.
| Species | lbs | N |
| Cherry, Red maple | 950 | 4,200 |
| Paper birch | 900 | 4,000 |
| Mahogany | 800 | 3,600 |
| Silver maple | 700 | 3,100 |
| Fir | 650 | 2,900 |
| Larch | 600 | 2,600 |
| Chestnut, Poplar | 550 | 2,400 |
350 to 500 is the semi-hard category, while woods below this are soft.
| Species | lbs | N |
| Pine (different variants) | 200-400 | 1,100-1,900 |
| Fir, Lime, Poplar, Willow | 200-350 | 900-1,600 |
| Balsa | 70 | 310 |
Balsa is so soft and light that it is suitable as a material for model aeroplanes.
While the Janka scale is a good measure of hardness, it does not directly test resilience to scratches or scuffing. Engineered or composite wood boards will also have different characteristics. Nevertheless, these measurements are a good guide to how long your cabinet, desk, shelf or flooring can serve you.
What about softwoods and hardwoods?
The definition of softwoods and hardwoods is based on biology, and while it is true to most hardwoods are actually harder than softwoods, it is not necessarily so. Hardwoods are from dicot trees, whose seeds have two embryonic leaves. Softwoods are, on the other hand, are species whose seeds are not enclosed, e.g. in pine cones (angiosperms).