Work out parts per billion instantly with clear inputs, formula shown and shareable results.
Parts per billion is a mass ratio scaled by 10^9, used where a concentration is far too small to read comfortably as a percentage. Half a milligram of contaminant in a kilogram of solution is 0.5 ppm or 500 ppb, and because water is close to 1 kg per litre, ppb also reads as micrograms per litre for dilute aqueous samples.
Parts per billion
ppb = (solute mass / solution mass) x 1,000,000,000
Relation to ppm
1 ppm = 1000 ppb
For dilute water samples, effectively yes, because one litre of water has a mass of about one kilogram. For other solvents you must use the actual density.
A 500 ppb result would be 0.00005% - a string of leading zeros that is easy to misread. ppb keeps trace figures readable.