PPM Calculator
A free ppm calculator that converts between parts per million, mg/L and percent — and works out the mass of solute you need for a target ppm in a given volume of water.
Enter a value and choose its unit to see the ppm, mg/L and percent equivalents.
What does ppm mean?
Parts per million (ppm) expresses concentration as the number of parts of a substance per one million parts of the whole mixture. It is the go-to unit for very dilute solutions — drinking water limits, chlorine dosing, nutrient solutions and trace contaminants — where percentages would be tiny, hard-to-read numbers.
The key relationships
Two simple conversions cover almost every ppm question:
- 1 ppm = 1 mg/L for dilute aqueous solutions, because 1 litre of water weighs about 1 kilogram (1,000,000 mg), so one part per million by mass is one milligram per litre.
- 10,000 ppm = 1%, so to convert ppm to percent you divide by 10,000 (and multiply by 10,000 to go the other way).
Mass for a target ppm
Because 1 ppm equals 1 mg/L, the mass of solute you need is just the target ppm multiplied by the water volume in litres: mass (mg) = ppm × volume (L).
Worked example
Suppose you want a 50 ppm chlorine solution in 20 L of water. The mass needed is 50 × 20 = 1000 mg, which is 1 g of chlorine. In percent terms, 50 ppm is 50 ÷ 10,000 = 0.005%, and it is also equal to 50 mg/L.
Related tools
Working in percentages instead? Use the percent solution calculator. To dilute a stock solution down to a target concentration, use the home dilution calculator.
Frequently asked questions
›What is ppm (parts per million)?
Parts per million (ppm) is a unit of concentration that describes how many parts of a substance are present in one million parts of the total mixture. A concentration of 1 ppm means one part solute for every 999,999 parts of everything else — for example, 1 milligram of a chemical dissolved in 1 kilogram of water. It is used for very dilute solutions where percentages would be awkwardly small.
›How do I convert ppm to mg/L?
For dilute aqueous (water-based) solutions, the conversion is one-to-one: 1 ppm equals 1 mg/L. This holds because 1 litre of water weighs almost exactly 1 kilogram (1,000,000 mg), so one part per million by mass is one milligram per litre. Enter a value in the converter above and it returns the mg/L equivalent instantly.
›How do I convert ppm to percent?
Divide the ppm value by 10,000, because 10,000 ppm equals 1%. So 50 ppm is 50 ÷ 10,000 = 0.005%, and 1% is 10,000 ppm. The converter above shows the percent equivalent alongside ppm and mg/L for any value you type.
›Is this ppm calculator free?
Yes. This ppm calculator is completely free, runs entirely in your browser, and needs no sign-up. Your numbers are never sent to a server.
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