Work out gas density instantly with clear inputs, formula shown and shareable results.
Rearranging PV = nRT with n = m/M gives density directly as PM/(RT). Air at one atmosphere and 25 C works out at 1.18 kg/m3. Because molar mass sits on top, a heavier gas is denser at the same conditions - carbon dioxide at 44 g/mol is about 1.5 times air, which is why it pools in low spaces.
Ideal gas density
rho = P x M / (R x T)
Molar volume
Vm = R x T / P
Less well. Near the critical point real gases deviate and a compressibility factor Z must divide the result.
Because that is how tables list it. The calculator converts to kg/mol internally to keep the density in SI units.