Convert Grain (gr) to Planck Mass (mₕ) instantly.
About these units
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.
Planck Mass (mₕ)
The Planck mass, approximately 2.176434 × 10⁻⁸ kilograms, occupies a unique position in theoretical physics. Unlike particle masses, it is derived entirely from fundamental constants—Planck's constant, Newton's gravitational constant, and the speed of light. The Planck mass represents a mass scale where quantum mechanical and gravitational effects become comparable. Although enormous relative to subatomic particles (roughly the mass of a dust grain), it is considered "natural" in that it emerges from pure physics rather than empirical observation. In theoretical studies of black holes, quantum gravity, string theory, and early-universe cosmology, the Planck mass marks a boundary beyond which existing models require unification. It is a conceptual rather than practical unit, yet it provides a profound insight into the structure of physical law.