**Bohr** is a unit of measurement of length. The definition for bohr is the following:

1 bohr is approximately equal to the Bohr radius of hydrogen

A **bohr radius** is the distance of a single hydrogen electron from its nucleus when this electron is making the smallest possible orbit with the lowest energy around its nucleus.

The value of a bohr radius is equal to 5.2917720859(36) × 10^{−11} metres (approximately 53 pm or 0.53 ångströms).

The symbol for bohr is

**a**_{0}Bohr is compatible with the

metre base unit.

*Please note: The equivalent value of bohr in SI units is an approximation.*