The amg unit for number density can be converted to the SI unit mol/m by the formula
where ≘ indicates correspondence, since the SI unit is of molar concentration and not number density.
The conversion factor (44.615...) is the Loschmidt number divided by the Avogadro constant.
The number density of an ideal gas at pressure p and temperature T can be calculated as 
where T = 273.15 K, and p = 101.325 kPa (STP before 1982).