The number of reflected light is a measure assigned by a gloss meter as a gloss unit (GU). It is a normalized quantity in which 100 GU is normally a perfect reflection at 60°, and 0° GU is a full diffusion.

 A gloss test gauges the reflective quality of a surface by casting light at a fixed angle and measuring the amount reflected. It defines the level of shine or dullness of a surface, and it is very crucial in coatings, automotive, and product finishing

 A gloss meter measures the amount of light reflected from a surface at a specific angle. It's commonly used to assess surface finishes such as paint, coatings, plastics, and paper for consistency, quality control, and visual appearance evaluation.