Molarity Calculator
Enter mass, molar mass, and volume to calculate moles, mass concentration, and molarity.
Inputs
g
g/mol
L
Results
Moles
—
Mass Concentration
—
Molarity
—
Step-by-Step
Enter values and click Calculate.
n = m / Mrc = m / VM = n / V = m / (Mr × V)
Use this Molarity Calculator to calculate moles, mass concentration, and molarity from the solute mass, molar mass, and final solution volume.
Molarity Formulas
Moles = mass ÷ molar mass
Mass concentration = mass ÷ solution volume
Molarity = moles ÷ solution volume
The direct molarity formula is:
Molarity = mass ÷ (molar mass × solution volume)
Enter mass in grams, molar mass in grams per mole, and final solution volume in litres.
Example
Suppose a solution contains 10 g of solute with a molar mass of 50 g/mol in a final volume of 2 L.
Moles = 10 ÷ 50 = 0.2 mol
Mass concentration = 10 ÷ 2 = 5 g/L
Molarity = 0.2 ÷ 2 = 0.1 mol/L
The solution therefore contains 0.2 mol of solute and has a molarity of 0.1 M.
Important Notes
- Use the final volume of the complete solution, not only the amount of solvent added.
- Convert millilitres to litres before calculating manually: 1,000 mL = 1 L.
- Use the molar mass of the exact compound, ion, or hydrate being measured.
- This calculator does not calculate molar mass from a chemical formula.
- It does not account for reagent purity, density, temperature effects, or laboratory measurement uncertainty.