Concentration converter between mg/l and ppm or ppb for liquids


If the solvent is water (density 1000kg/m3), tick the box below. If it is not water, we need to enter the density of the solvent. Then simply enter the concentration in the known units (mg/l, ppm or ppb).

The solvent is water


The concentration expressed in mg/l is a measure of the amount of mass (in milligrams) of solute per volume (in litres) of solvent.

The ppm (parts per million) is, as the name suggests, the number of parts of solute per million parts of solvent. Similarly, the ppb (parts per billion) are the parts of solute per billion parts of solvent. It should be noted that the billions here are american billions, i.e. one billion would be one thousand millions, so 1ppm = 1000ppb. When we talk about concentrations in ppm or ppb, we should also indicate whether we are talking about mass or volume. In the case of solutions, the concentration is normally expressed in mass, which is what we consider on this page.

The conversion between these concentration units is done by the following formula:
    mg/l =ppm x density /1000
density in grams/litre (or kg/m3)

When the solvent is water the density is approximately 1000 g/l (at 5°C) so 1 mg/l = 1 ppm. This simplifies the calculation a lot, however, this value value is only accurate when the temperature is 5ºC, since water density varies with temperature varies with temperature. However this simple equivalence is usually used. Water density can also vary with salinity and the concentration of other dissolved substances.