Parts Per Million (ppm)

A part per million is one of aty in one million of another quantity. Parts per million is abbreviated to "ppm". To convert a concentration from v/v to ppm the concentration must be in ml/ml, L/L, etc. then multiply by 10⁶ to get ppm v/v.

In the same way w/w concentration can only be converted to ppm using the factor "10⁶" if the concentration is expressed in grams per gram (g/g),
kilograms per kilograms (kg/kg), etc.