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CalcSpectrum

Molarity Calculator

Calculate molar concentration (mol/L) from mass of solute, molecular weight, and solution volume.

Free to use · Instant results

Calculator Inputs

Mass of the dissolved solute, in grams. Must be zero or a positive number.

Molecular weight of the solute, in grams per mole. Must be a positive number.

Total volume of the solution, in liters. Must be a positive number.

Molar Concentration
0.10
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About these results

CalcSpectrum calculators produce automated estimates using established formulas and the specific values you enter. Because real-world outcomes depend on input accuracy, mathematical assumptions, and rounding conventions, please verify critical figures with an appropriately qualified financial, tax, medical, legal, or other professional, as relevant.

How It's Calculated

Formula

M=massgMWg/mol×volumeLM = \frac{\text{mass}_g}{\text{MW}_{g/mol} \times \text{volume}_L}

Molarity (M) expresses the concentration of a dissolved solute as moles of solute per liter of solution. First, mass of solute is divided by molecular weight to get moles. Then moles are divided by solution volume in liters to get molarity in mol/L. This calculator accepts mass and molecular weight directly — it does not parse a chemical formula like "NaCl" into a molecular weight for you.

Worked Examples

5.844 g solute, MW 58.44 g/mol, 1 L solution

  1. Moles = 5.844 / 58.44 = 0.1 mol
  2. Molarity = 0.1 / 1 = 0.1 mol/L

10 g solute, MW 40 g/mol, 0.5 L solution

  1. Moles = 10 / 40 = 0.25 mol
  2. Molarity = 0.25 / 0.5 = 0.5 mol/L

Frequently Asked Questions

Does this calculator parse chemical formulas like "NaCl"?

No. Enter the molecular weight directly in grams per mole. Looking up a molecular weight from a chemical formula is handled by a separate Molecular Weight Calculator.

Why must molecular weight and volume be positive?

Molecular weight and volume both appear in the denominator of the molarity formula, so a zero or negative value would make the calculation undefined. Mass can be zero (yielding a molarity of zero) but not negative.

What units does this calculator use?

Mass is in grams (g), molecular weight is in grams per mole (g/mol), volume is in liters (L), and the result is in moles per liter (mol/L).