Molarity calculator

Find the molarity of a solution from mass, work out how many grams to weigh for a target concentration, solve the c = n/V triangle, or plan a dilution. The molar-mass box accepts a chemical formula like NaCl or CuSO4·5H2O — it works out the molar mass for you. Everything runs in your browser.

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Result —

How it works

molarity (mol/L) = moles of solute ÷ volume of solution (L)

moles = mass (g) ÷ molar mass (g/mol)

dilution: C₁ × V₁ = C₂ × V₂

Molarity (M, mol/L) is the number of moles of solute per litre of solution — not per litre of solvent. To get moles from a mass, divide by the molar mass; this tool can read the molar mass straight off a chemical formula, adding up the standard atomic weights of each element (so NaCl → 58.44 g/mol).

Dilution keeps the moles of solute constant while you add solvent, so C₁V₁ = C₂V₂. Solve for V₁ to find how much concentrated stock to measure out, then top up to the final volume V₂. You can only dilute, never concentrate, so C₂ must be lower than C₁.