For some projects, you know you want something stronger than say, a pine. That is why it is important to know the density of wood, which is the measurement of weight per unit volume in wood.
It is the principle method of measuring a wood's strength and can also help you predict how you are going to need to work with it. If you have got yourself a dense wood, you can bet it will probably shrink and swell more than other less dense woods and create some hurdles during the drying process. But, should you be using wood for fuel, it is best to go with a dense wood as it will burn longer and more efficiently. See how knowing a wood's density can be useful?
Density is not the only factor in relation to a wood's mass that can be useful to be knowledgeable about. Specific Gravity, or the ratio of density of the substance to the density of a standard substance like water, can help a woodworker maximize his potential with his material. Some call this the density index, which helps measure the ratio of a wood from oven-dry weight, which is very dry, to a wood that is rich with water content.
Having this type of information can be very helpful for a woodworker. Should he need to know how long to dry the wood or how much room the wood will need to swell and shrink, he can appropriately fashion his project for those incidents. But not all woods are alike –that's for sure. Take the following woods, for example. A very large block of a soft, dry wood like Balsa may weigh the same as a small, moist block of Rosewood. That is because rosewood has a much higher moisture content than the other wood, making it stronger, but often more difficult to work with.
Density index also helps to prove that terms like "hardwood" and "softwood" can be misleading. These two types of woods overlap on much of the index, and only a few woods really vary outside of the general density of most woods.