PPM to Molarity Converter

Convert parts per million to molarity (mol/L) from the solute’s molar mass, with density for non-aqueous cases.

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Concentration (ppm) Molar mass (g/mol) Density (g/mL, 1 for water)

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Molarity

Millimolarity (mmol/L)

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Milligrams per litre (mg/L)

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Assumption

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How to use this tool

Enter the ppm value

Enter the concentration in parts per million.

Enter the molar mass

Enter the solute’s molar mass in g/mol.

Enter the density

Enter the solution density, or leave 1 for water.

Read the molarity

Read mol/L, mmol/L and mg/L.

Molarity = ppm × density ÷ (molar mass × 1,000); for water, density ≈ 1 g/mL so ppm ≈ mg/L.

58,440 ppm of NaCl (molar mass 58.44 g/mol) in water is 1 mol/L.

Uses the mass definition of ppm; gas-phase volume ppm and highly concentrated solutions need their own conversions.

Parts per million by mass: milligrams of solute per kilogram of solution.

Molarity is per litre of solution, so a mass ratio needs density to become a per-litre amount; for water the factor is about 1.

Only when density is 1 g/mL. For denser or lighter solutions the two differ by the density factor.

For gases it sometimes is; this tool uses the mass definition, which is standard for dissolved solids.

The solute’s molar mass in g/mol, including any waters of hydration in the weighed form.