Solution ppm Calculator
Parts per million expresses very small concentrations cleanly, which is why it is the standard unit for trace contaminants, water treatment, and dosing. This calculator takes the mass of solute and the mass of the whole solution, both in the same unit, and returns the concentration in parts per million, parts per billion, and percent by mass. It is mass-based, so it is independent of temperature and works for any solvent as long as the two masses share units.
Parts per million formula
mass fraction = mass solute / mass solution
ppm = mass fraction * 1,000,000
ppb = mass fraction * 1,000,000,000
percent by mass = mass fraction * 100
Both masses must use the same unit (grams, kilograms, etc.) because the ratio is dimensionless. One ppm is one milligram of solute per kilogram of solution.
Worked example
- 0.5 g of solute in 1,000 g of solution gives a mass fraction of 0.0005.
- 0.0005 times 1,000,000 = 500 ppm.
- That is 500,000 ppb and 0.05 percent by mass.
- For dilute water at 1 kg per L, 500 ppm is about 500 mg per litre.
- One percent equals 10,000 ppm; 1 ppm equals 1,000 ppb.
Parts per million: frequently asked questions
What does ppm mean?
Parts per million (ppm) is a dimensionless concentration unit equal to one part of solute per million parts of total solution by mass. One ppm is the same as 1 milligram of solute per kilogram of solution, or for dilute water-based solutions, roughly 1 milligram per litre.
How is ppm calculated by mass?
Divide the mass of solute by the total mass of solution and multiply by one million: ppm = (mass solute / mass solution) times 1,000,000. Both masses must be in the same unit. This calculator also reports parts per billion (times one billion) and percent by mass.
Is 1 ppm the same as 1 mg/L?
For dilute aqueous solutions it is very nearly so, because the density of dilute water is close to 1 kilogram per litre, so 1 mg per kg equals about 1 mg per litre. For concentrated solutions or non-water solvents the densities differ and the equivalence no longer holds exactly.
How do ppm, percent and ppb relate?
One percent by mass equals 10,000 ppm, and 1 ppm equals 1,000 ppb. So a 0.5 percent solution is 5,000 ppm, which is 5,000,000 ppb. This calculator shows all three so you can pick the most convenient scale for your concentration.
Official sources
- U.S. EPA: drinking water contaminant limits in ppm and mg/L.
- NIST: unit and concentration conventions.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.