PPM Calculator
Parts per million and per billion from the mass of a solute and its solution, or the volume of a gas in air, with mg/L, percent and molarity.
Result…
How it's calculated
ppm = part ÷ whole × 10⁶ ppb = part ÷ whole × 10⁹ Percent = ppm ÷ 10,000 mg/L = ppm (mg/kg) × density (kg/L) Molarity (mol/L) = mg/L ÷ 1,000 ÷ molar mass (g/mol)
Parts per million is a ratio: one part of a substance for every million parts of the whole, measured the same way. By mass it is milligrams per kilogram; for gases it is normally by volume (ppmv), millilitres of gas per cubic metre of air. In water, a litre of a dilute solution weighs about a kilogram, so ppm and mg/L are nearly the same number, but only while the density stays close to 1 kg/L. Dividing mg/L by 1,000 and by the molar mass gives the molarity. Mass units are converted exactly (1 lb = 453.59237 g, 1 oz = 28.349523125 g) and 1 ft³ = 28.316846592 L.
Your numbers, step by step
About the PPM calculator
This ppm calculator turns a mass or volume ratio into parts per million and parts per billion. Enter the mass of a dissolved substance and the total mass of the solution or sample, and it gives ppm by mass (the same as mg/kg), ppb and the percentage. For gases, choose volumes instead: the result is ppm by volume (ppmv), which is millilitres of gas per cubic metre of air. If you already have a ppm value, it converts it to mg/L using the density you enter, about 1 kg/L for dilute solutions in water, and to molarity when you add the molar mass. Water testers, pool and aquarium keepers, lab students and anyone reading an air quality figure use these conversions. The steps show each unit change and division, so you can follow how the number was reached.
How to use it
- Under “Work from”, choose “Masses (w/w)” for a solution or solid sample, “Gas volumes (v/v)” for a gas in air, or “A ppm value” to convert a figure you already have.
- Enter the “Mass of the solute” and the “Total mass of the solution or sample”, each with its unit. The total includes the solute.
- Check the “Density of the solution”: leave it at 1 kg/L for dilute water solutions, or enter the measured density.
- To get molarity, set “Molarity too” to “From molar mass” and enter the “Molar mass of the solute” in g/mol.
- Read ppm, ppb, percent, mg/kg, mg/L and, if asked, mol/L and mmol/L.
Worked example
50 mg of sodium chloride is dissolved to make 2 kg of solution. 50 mg is 0.05 g and 2 kg is 2,000 g, so ppm = 0.05 ÷ 2,000 × 10⁶ = 25 ppm, or 25,000 ppb and 0.0025%. At a density of 1 kg/L that is 25 mg/L, and with a molar mass of 58.44 g/mol the molarity is 25 ÷ 1,000 ÷ 58.44 = 0.000428 mol/L (0.428 mmol/L).
Updated
Questions people ask
How do I calculate ppm from grams?
Divide the mass of the substance by the total mass of the sample, both in the same unit, and multiply by 1,000,000. 0.05 g in 2,000 g is 25 ppm.
Is 1 ppm the same as 1 mg/L?
Only for dilute solutions in water, where a litre weighs close to 1 kg. ppm by mass is mg per kg, so mg/L = ppm × density in kg/L; seawater or a strong brine gives a noticeably different number.
How do I convert ppm to molarity?
Turn ppm into mg/L with the density, divide by 1,000 to get g/L, then divide by the molar mass in g/mol. The molarity calculator goes on from there to the mass you need to weigh out.
What is the difference between ppm and ppmv?
ppm usually means by mass for liquids and solids, while gas concentrations in air are given by volume (ppmv). Both volumes must be at the same temperature and pressure for ppmv to be meaningful.
How many ppb is 1 ppm, and what is 1 ppm as a percentage?
1 ppm is 1,000 ppb and 0.0001%. Going the other way, 1% is 10,000 ppm.
Can this tell me whether a level is safe?
No. It only converts units. Limits for drinking water, air and food are set by regulators and vary by country and substance, so check the rule that applies where you are, or ask a water or environmental health professional.