ppm to molarity calculator
For dilute aqueous solutions one ppm is one milligram per litre, because a litre of water weighs a kilogram.
ppm
g/mol
Molarity
0.004 277 89mol/L
- Same concentration
- 4277.89 micromol/L
- Mass concentration
- 250 mg/L
Show the working
- Concentration = 250
- Molar mass = 58.44
- Mass concentration = 250 = 250
- Molarity = 250 / 1000 / 58.44 = 0.004 277 89
- Same concentration = 0.004 277 89 * 1e6 = 4277.89
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- 1 ppm in water = 1 mg/L
- molarity = (mg/L / 1000) / molar mass
The equivalence between ppm and mg/L only holds when the solution density is 1.00 kg/L, which is true for dilute water at room temperature and not much else.
For gases in air, ppm is by volume rather than by mass, and the arithmetic is different.