Ångström (Å)

How to read it

The IUPAC Green Book says the distances between atoms are commonly given in ångströms, where 1 Å = 10⁻¹⁰ m = 0.1 nm = 100 pm, and calls it a non-SI unit. OpenStax’s Chemistry 2e says the visible region of the spectrum is usually given in wavelengths in nanometres or angstroms, with 1 Å = 0.1 nm. NIST’s Guide for the Use of the SI (2008) lists the ångström among the non-SI units accepted for use with the SI, and its advice on conversions is that values in ångströms, such as the wavelengths of visible laser light, are usually converted to nanometres, not metres. Unicode’s chart says the unit is named after A. J. Ångström, a Swedish physicist.

Also searched as: Å, angstrom, angstrom symbol, ångström symbol, Å unit, A with a circle on top.

Typing Å

Unicode has an ANGSTROM SIGN (U+212B) for the unit, but its chart says the preferred character is the letter Å (U+00C5), the capital A with ring above, and treats the two as the same. NIST and the Green Book spell the unit ångström; OpenStax writes angstrom.

Look-alikes

Without the ring, an upright A is the Ampere (A), the unit of electric current.