One part per million is one part of solute per one million parts of solvent. It is a dimensionless unit. The equivalency between ppm and % (percent) is as follows:
1 ppm = 0,0001%
10.000 ppm = 1%
As water density is 1 kg/m3 (This is the value normally considered although it varies slightly with temperature, you can calculate it
with accuracy with our water density calculator), one ppm
is equivalent to 1 milligram of something per liter of water (mg/l). In general it is equivalent to 1 mg/kg.
ppb (parts per billion)
One part per bilion is one part of solute per one billion parts of solvet.
1000 ppb = 1ppm = 0.0001%
1 ppb = 0.001ppm = 0.0000001%