Density of Air
Derivation of a Reduced Equation for the Density of Air
PO Box 4394
Seven Corners, VA 22044-0394
Starting from published equations and first principles for the density of humid air as a function of
partial pressure of dry air and of water vapor with equations for total pressure and a model for relative humidity,
a derivation is presented here, step by step, with justification for each step,
leading the reader to a final equation in condensed computationally efficient form for
the density of air in kilograms per cubic meter as a function of three observable variables only:
barometric pressure in Pascals,
relative humidity in percent relative humidity, and
temperature in degrees Celcius,
resolving physical constants to numerical constants
compatible with measurements of common accuracy and precision.
Then, a version of the final equation suitable for Copy and Paste into computer code is given.