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Safety Checklist Program for Schools


October 2003
DHHS (NIOSH) Publication Number 2004-101
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Conversion Calculator

“mg/m3 to ppm” or “ppm to mg/m3

The conversion equation is based on 25 ºC and 1 atmosphere:
X ppm = (Y mg/m3)(24.45)/(molecular weight)


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).