Parts Per Billion Calculator
Calculate parts per billion (ppb), a way of expressing extremely dilute concentrations often used for trace contaminants in water, air, or soil.
What parts per billion means
Parts per billion (ppb) is a unit used to express extremely small concentrations, such as trace contaminants in drinking water, pollutants in air, or minor impurities in a chemical sample. One ppb means one part of solute for every one billion parts of solution by mass (equivalent to micrograms per kilogram, or roughly micrograms per liter for dilute water-based solutions).
The formula
Parts per billion is calculated as ppb = (mass of solute ÷ mass of solution) × 1,000,000,000. This calculator accepts solute mass in milligrams and total solution mass in kilograms, converts both to consistent units internally, and reports the result in ppb along with the equivalent ppm and mass percent for comparison.
Note: For dilute aqueous solutions near room temperature, 1 kg of solution is approximately 1 liter, so ppb (mass basis) is commonly treated as roughly equal to micrograms per liter. This tool is for general chemistry and environmental education purposes, not for regulatory compliance testing.