1 ppm is equal to how many mg/nm3?
Parts per million and parts per billion may be converted from one to the other using this relationship: 1 part per million = 1,000 parts per billion. For water, 1 ppm = approximately 1 mg/L (also written as mg/l) of contaminant in water, and 1 ppb = 1 ug/L (also written as ug/l).