Hardness

• The Janka scale is the most often used comparative figure when evaluating woods. It rates the hardness of wood as the amount of force necessary to embed an object in a piece of wood. White oak is measured at 1360 pounds of force. Red elm only requires 860 pounds of force, making this the softer of the two woods.
  
  

Density

• The density of wood is an expression of the material's weight per cubic foot. This measurement of density is used by woodworkers to determine how well the wood cuts, joins and finishes. Red elm has a density of 0.53 while white oak is measured at 0.68, the heavier of the two densities.
  
  

Using Hard Woods

• Knowing the comparative values of these two woods enables you to decide if the wood is appropriate to your task. If the choice is for a flooring material, the white oak will withstand scratching and denting a little bit better than the red elm. Furniture makers will look at the wear on cutting tools and finishing materials when selecting the harder material over the softer.