PPM Concentration Calculator

How it is calculated

Parts per million is the fraction of solute in the whole solution, scaled up by a million: ppm = solute / solution × 1,000,000. Both amounts must be in the same unit, for example grams, so the unit cancels. The tool also shows the same fraction as a percentage, percent = solute / solution × 100, where 1 ppm is 0.0001%.

The solution is the total, solute plus solvent, not the solvent alone. It must be greater than zero, and the solute cannot be negative. The solute may be larger than the solution only by mistake, because the tool does not stop it and would show a value above 1,000,000 ppm. The calculation is a mass ratio. For dilute water solutions, 1 mg per litre is often treated as about 1 ppm, but that shortcut depends on the solution having a density close to water.

Common mistakes

• Using the solvent mass as the denominator. The denominator is the whole solution, solute included, though for very dilute cases the difference is tiny.
• Mixing units, such as milligrams of solute and kilograms of solution. Convert both to the same unit first, or the answer is off by a factor of a million.
• Treating mg/L as exactly ppm for any liquid. That holds only when the solution density is close to 1 kg per litre.
• Confusing ppm with percent. 1% is 10,000 ppm, so a 0.1500% result means 1,500 ppm.
• Mixing mass and volume, such as grams of solute against millilitres of solution, which is not a mass ratio.