Convert Bohr Radius (a₀) to Barleycorn (barleycorn) instantly.
About these units
Bohr Radius (a₀)
The Bohr radius, equal to approximately 5.29177 × 10⁻¹¹ meters, is the most probable distance between the electron and nucleus in the ground state of hydrogen according to the Bohr model. While modern quantum mechanics has evolved far beyond the Bohr model, the radius remains a remarkably accurate approximation for average atomic dimensions. The Bohr radius acts as a natural "yardstick" for the size of atoms and is frequently used in atomic physics and quantum chemistry. Many atomic properties — orbital sizes, electron probability distributions, and energy levels — are conveniently expressed in multiples of the Bohr radius. Because it reflects fundamental constants, including Planck's constant and the electron charge, the Bohr radius also appears in theoretical analyses of physical systems and helps unify atomic physics concepts across different contexts.
Barleycorn (barleycorn)
The barleycorn is an English unit, approximately 1/3 inch (8.47 mm), originally based on the length of a grain of barley. It served as a small-scale measure in tailoring, shoe sizing, and other crafts. In particular, the English shoe size system was historically based on barleycorns, with increments in size corresponding to single barleycorn units. This unit exemplifies the anthropometric and agronomic origins of measurement. Even today, the barleycorn's influence persists in the traditional shoe sizing system in the UK and the US, providing continuity with historical practices.