Convert Angstrom (Å) to A.U. of Length (a.u.) instantly.
About these units
Angstrom (Å)
The ångström, equal to 10⁻¹⁰ meters, is traditionally used to measure atomic scales, bond lengths, and wavelengths of electromagnetic radiation, particularly in the X-ray and ultraviolet regions. Although not an SI unit, the ångström persists because it aligns conveniently with many natural atomic dimensions — hydrogen's typical bond lengths, for example, are close to 1 Å. Scientists in crystallography, astronomy, materials science, and spectroscopy routinely use ångströms when describing the spacing between atoms in a crystal lattice or the wavelength of certain spectral lines. The convenience comes from avoiding unwieldy decimals: instead of writing 0.154 nm, one may write 1.54 Å. While modern research increasingly prefers SI nanometers or picometers, the ångström remains deeply embedded in scientific traditions and continues to serve as a practical shorthand for atomic-scale measurements.
A.U. of Length (a.u.)
The atomic unit of length, also known as the Bohr radius unit in atomic units, is approximately 5.29177 × 10⁻¹¹ meters. It is defined as the radius of the lowest-energy orbital of the hydrogen atom, providing a natural scale for describing atomic and quantum mechanical systems. Atomic units were devised to simplify equations in quantum chemistry and atomic physics by normalizing fundamental constants such as electron charge, Planck's constant, and electron mass to 1. In this system, many equations become dimensionless and far easier to manipulate mathematically. The atomic unit of length is essential in molecular orbital calculations, quantum simulations, and the study of electron behavior in atoms and molecules. Its use reflects an approach to physics in which units are chosen to match the natural scales of the systems being studied.