Gr is a unit of measurement used in the field of chemistry and pharmacology to denote the weight of a substance. It stands for "grain," which is a traditional unit of mass equal to approximately 64.8 milligrams. The grain is often used to measure small quantities of solid substances, particularly in the formulation of medications. In addition to its use in science, Gr is also commonly found in the context of firearms and ammunition, where it indicates the weight of bullets or gunpowder. Understanding Gr is essential for accurate dosing in medicine and for ensuring proper performance in shooting sports.