Concentration Converter — Convert Between Molarity, ppm, % and More

Concentration turns up in chemistry, environmental science, medicine, food safety, and water treatment — and every field has its own preferred units. A water quality report gives you results in mg/L; a lab protocol lists things in mM; a food label uses %. The CalcHub Concentration Converter translates between them without requiring you to remember the conversion factors for every pair.

Units the Converter Handles

Unit	Full Name	Common In
mol/L (M)	Molarity	Chemistry labs
mmol/L (mM)	Millimolarity	Biochemistry
μmol/L (μM)	Micromolarity	Pharmacology
g/L	Grams per liter	Industrial
mg/L	Milligrams per liter	Water quality (≈ ppm for water)
μg/L	Micrograms per liter	Environmental (≈ ppb for water)
% w/v	Weight per volume	Food, pharma
% w/w	Weight per weight	Solid mixtures
ppm	Parts per million	Environmental, water
ppb	Parts per billion	Trace analysis

How to Use It

1. Open the Concentration Converter.
2. Enter the value and select the starting unit.
3. For conversions involving molarity, you'll need the molar mass — enter it in g/mol.
4. The result appears in all target units simultaneously.

The molar mass requirement is unavoidable for M ↔ g/L conversions because molarity depends on what the substance actually is, not just how concentrated the solution is.

Key Conversions

For a substance with molar mass M (g/mol):

mol/L × M (g/mol) = g/L

g/L × 1000 = mg/L

mg/L ≈ ppm (for dilute aqueous solutions where density ≈ 1 g/mL)

Example: Convert 0.05 M NaCl (M = 58.44 g/mol) to mg/L: 0.05 × 58.44 = 2.922 g/L = 2922 mg/L

The ppm Nuance

"ppm" means different things in different contexts:

• In liquids (water): mg/L (mass of solute per volume of solution)
• In gases: μmol/mol or μL/L (volume fraction)
• In solid mixtures: mg/kg (mass fraction)

The calculator asks for context so it applies the right definition.

Tips

• % w/v is not the same as % w/w. For solutions where density ≠ 1 g/mL, the two diverge. A 10% w/v solution contains 10 g of solute per 100 mL, regardless of solvent density.
• ppb vs μg/L. For dilute water samples, 1 ppb ≈ 1 μg/L. This approximation breaks down for dense solvents.
• Molar mass is substance-specific. The same 100 mg/L concentration of glucose vs. NaCl represents very different molar concentrations because their molar masses differ (180 vs 58 g/mol).

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When does mg/L exactly equal ppm?

When the solution density is exactly 1 g/mL, which is approximately true for dilute aqueous solutions at room temperature. In that case, 1 ppm = 1 mg/kg ≈ 1 mg/L. For other solvents or concentrated solutions, use the actual density for accurate conversion.

How do I convert ppm to molarity?

You need the molar mass: M (mol/L) = ppm (mg/L) ÷ (molar mass × 1000). For example, 100 ppm of NaCl = 100 ÷ (58.44 × 1000) = 0.00171 mol/L = 1.71 mM.

What's the difference between w/v and v/v percent?

w/v (weight/volume) is grams of solute per 100 mL of solution — used for solids dissolved in liquids. v/v (volume/volume) is mL of solute per 100 mL of solution — used for liquid-liquid mixtures like ethanol in water.

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Related calculators: Molarity Calculator · Dilution Calculator · pH Calculator