The conversion equation is based on 25 ºC and 1 atmosphere:

X ppm = (Y mg/m³)(24.45)/(molecular weight)

or

Y mg/m³ = (X ppm)(molecular weight)/24.45

Fill in either the "ppm" value (X) or the "mg/m³" value (Y) AND the molecular weight of the compound. Then press the "Calculate" button.

ppm: mg/m³: molecular weight:

Remember to consider significant digits in your use of the answer.

To determine molecular weight, add the atomic weights of all atoms present in the chemical formula for a particular substance. Periodic Table (courtesy of Los Alamos National Laboratory).