Molarity Calculator

Molarity (molar concentration) expresses how many moles of solute dissolve in each liter of solution — not solvent alone. Lab benches worldwide label bottles "0.1 M HCl" or "1.0 M NaOH" using this unit. Titrations, electrochemistry, and biochemical assays specify molarity because reaction stoichiometry counts moles, not grams.

Molarity definition:

M = n / V

Where M is molarity in mol/L (M), n is moles of solute, and V is solution volume in liters. Rearranged: n = M × V and V = n / M. Mass from molarity: m = M × V × M_r where M_r is molar mass in g/mol.

Enter any two of molarity, moles, and volume, or mass with molar mass and volume for direct solution prep. Always use total solution volume after dissolving — adding 58.44 g NaCl to water and diluting to 1.00 L yields 1.00 M NaCl, not the volume of water alone. Temperature affects volume slightly; volumetric glassware is calibrated at 20°C.

Worked example: Prepare 250 mL of 0.500 M NaCl. n = M × V = 0.500 × 0.250 = 0.125 mol. Mass = 0.125 × 58.44 = 7.31 g NaCl. Dissolve and dilute to the 250 mL mark. A 0.100 M HCl stock has n = 0.100 mol/L; taking 50 mL (0.050 L) contains 0.0050 mol HCl — use the dilution calculator for further weakening.

Chain to molar mass for mass-to-mole conversion, dilution for C₁V₁ = C₂V₂ problems, and pH for acid-base strength at known concentration. Molality and mole fraction handle special cases but molarity dominates general aqueous lab work.