Core PPM formula
The general mass-based formula is PPM = solute mass divided by solution mass, using compatible units, multiplied by one million.
A practical equivalent for dilute water is PPM = milligrams of solute per liter of water when density is close to 1 kg/L.
Choosing the right formula
Water, gas, solution, and manufacturing calculators use different forms of PPM because the underlying measurement is different.
Before calculating, identify whether the input is a mass concentration, volume ratio, percent concentration, EC reading, or defect rate.
Checking your result
A result should include the output unit, assumptions, and enough intermediate steps to verify the calculation.
If the result looks unexpectedly large or small, check whether the input units were mg, g, L, kg, percent, or PPB.
Frequently asked questions
What is the easiest PPM formula?
For dilute water, PPM is often calculated as mg/L.
Can one formula handle every PPM calculation?
No. Gases, liquids, percent conversions, and defect rates use different relationships.