Average Roughness (Ra) is one way to measure the roughness of a particular surface. The algorithm for Ra determines the average length between the valleys and peaks across a surface as well as the deviation from the mean surface line across that whole measured surface. All extreme outlier points of measurement are neutralized in the calculations involved in Average Roughness (Ra) so they do not significantly impact the final measurement. Ra has the advantages of being a simple and consistent parameter of surface roughness. Average Roughness (Ra) is the most commonly used parameter of surface texture in North America, as opposed to Mean Roughness Depth (Rz), which is used most commonly in Europe. Back to entire glossary
