Measurement angle refers to the angle between the incident light on a surface and the line perpendicular to the surface at the point of incidence. In specular reflection the incident and reflected angle are identical.

Typically, three measurement angles (20°, 60°, and 85°) are used to cover the majority of industrial coatings applications (Figure 1). The angle is selected based on the anticipated gloss range. Some measurement instruments offer the option to measure multiple angles at the same time.