Mean Roughness Depth (Rz) is one way to measure the roughness of a particular surface. The algorithm for Rz takes the vertical distance between the lowest valley and the highest peak from five different sample lengths and then averages these five distances. All extreme outliers have an enormous impact on the final measurement when using the Rz algorithm. Due to alterations over the years, Rz can be measured through three different calculations. It is important to ensure you know which algorithm you are using when calculating the Rz of a surface. Mean Roughness Depth (Rz) is the most commonly used parameter of surface texture in Europe, as opposed to Average Roughness (Ra), which is used most commonly in North America. Back to entire glossary
