Loschmidt Constant

Number density of an ideal gas at standard temperature and pressure, the 19th-century counting of air.

Specifications & Metrics

symbol

n0

status

Exact — exact via the 2019 SI

value

2.686780111 × 10²⁵ m⁻³

Relative Scale in Constants

Core Principles & Analysis

• Exactly 2.651 6 × 10²⁵ molecules per cubic metre in the 2019 SI.
• Loschmidt estimated molecular size from kinetic theory before molecules were accepted.
• Avogadro's number divided by the molar volume of an ideal gas at the same conditions.