Ra and RMS Surface Roughness Measures

Aug 23, 2016

RMS (Root Mean Square) and Ra (Roughness Average) are both measures of surface roughness. RMS calculates the Root Mean Square of the surface’s microscopic peaks and valleys. Ra takes the average of the peaks and valleys. They use the same height measurements. The RMS value will be affected more by a single or few large peaks (flaws) than will the Ra value.