Convert Point (pt) to Bohr Radius (a₀) instantly.
About these units
Point (pt)
A point is a typographic unit traditionally equal to 1/72 of an inch (in digital typography) or 0.352777 mm. Historically, however, the point system varied widely across regions and printing houses. In the era of metal movable type, each foundry often produced its own proprietary sizes, making typefaces and point values incompatible between printers. The modern point was standardized largely due to the demands of the publishing industry and later digital systems, especially PostScript and desktop publishing software. The point became essential because typography requires extremely fine control over letter height, line spacing, and layout—far beyond what conventional measurement systems could easily express. Designers and typesetters rely on points to specify the sizes of fonts, the spacing between lines (leading), and the thickness of rules or strokes. In digital environments, the point remains foundational even though screen resolutions vary. Software uses points as virtual units that are converted into pixels depending on display density. Thus, the point bridges the traditional world of print with modern digital rendering, maintaining continuity in the long history of written communication.
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.