Convert Milligram (mg) to Grain (gr) instantly.
About these units
Milligram (mg)
A milligram is one-thousandth of a gram and essential for measuring extremely small masses with precision. Pharmacology relies heavily on milligrams to dose medications safely and consistently—especially potent drugs where differences of a few milligrams can be critical. In chemistry and laboratory science, milligrams are used to weigh reagents, catalysts, micro-samples, and test materials. Environmental science uses milligrams per liter or milligrams per kilogram to describe concentrations of contaminants. Its small size makes the milligram ideal for fields requiring strict quantitative control, and its stability within the metric system ensures predictable conversions during calculations.
Grain (gr)
The grain, defined as exactly 64.79891 milligrams, is one of the oldest units of mass still in limited use today. Derived from the weight of average cereal grains such as barley or wheat, it became a universal tiny unit used across Europe for coins, medicine, and gunpowder. The grain persists in firearms and ammunition manufacturing because bullet weights are still listed in grains (e.g., a "150-grain bullet"). Reloaders and ballistic engineers rely on the grain as a fine unit suitable for measuring powder charges and projectile masses. It is also used in traditional gold and silver transactions, linking it to the troy system. The grain's longevity highlights how ancient agrarian measures can remain embedded in modern technological practices.