ChemicaLife

Molarity Calculator

Three calculation modes · Unit aware

Calculate molarity from moles or solute mass, or calculate the solute mass required to prepare a target molar concentration. Every result shows the formula and normalized SI inputs.

Important: Use the final solution volume—not simply the amount of solvent added. This calculator does not determine whether a formulation is safe, stable or appropriate.

ResultSelect a mode and enter the valuesNormalized inputs and calculation steps will appear here.

Core molarity formulas

From moles

M = n ÷ V

M is mol/L, n is amount in moles, and V is final solution volume in litres.

From mass

M = m ÷ (Mr × V)

Convert solute mass to moles using its molar mass before dividing by volume.

Prepare a solution

m = M × V × Mr

This returns the theoretical solute mass needed for the specified final volume.

Frequently asked questions

Is molarity the same as molality?

No. Molarity is amount of substance per volume of solution. Molality is amount of substance per mass of solvent.

Should I enter solvent volume or final solution volume?

Enter final solution volume. Dissolving a solute can change volume, so adding 1 L of solvent does not necessarily make exactly 1 L of solution.

Does purity affect the required mass?

Yes. The theoretical mass assumes 100% assay and the exact formula represented by the molar mass. Apply a purity or hydrate correction only when an authoritative protocol or certificate provides it.

Source and related calculators

The definition follows the IUPAC quantity amount concentration. Always confirm formula, hydration state and assay before laboratory preparation.