What is the standard unit for measuring surface roughness in the metric system?

The standard unit for measuring surface roughness in the metric system is micrometers. This unit is widely accepted for expressing surface finish because it aligns with the scale of roughness typically encountered in machining and manufacturing processes.

Surface roughness values can often be quite small, leading to the need for a unit that can precisely represent these dimensions. Micrometers provide a comprehensible scale that is both practical for measurement and easily comparable across various components and surfaces. While microinches, nanometers, and millimeters have their uses in specific contexts, micrometers are the preferred choice in industry standards for quantifying surface roughness.