Ra (Roughness Average)

Ra, or Roughness Average, is a measurement used to describe how smooth or rough a surface is. It calculates the average height difference between the highest peaks and lowest valleys across a specific area, providing a single number that quantifies surface texture. A lower Ra value indicates a smoother surface, while a higher Ra suggests more roughness. This measurement is important in industries like manufacturing and engineering, where surface smoothness can impact performance, appearance, or durability of parts and materials.