Molarity Calculator
Calculate the molarity of a solution knowing the mass, volume and molar mass.
Tip: For dilution: M₁V₁ = M₂V₂ — the universal formula for calculating dilutions in the lab.
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About this digital tool
The molarity calculator finds the molarity (M), the mass of the substance or the volume of the solution when two of the three quantities are known. Choose what you are looking for, enter the molar mass (g/mol) and the known values and get the result with the formula used.
Molarity shows how many moles of the substance are in a litre of solution: M = n ÷ V, where n = m ÷ MM. If we dissolve 5.85 g of NaCl (MM = 58.5 g/mol) in 0.5 L of water, the moles are 5.85 ÷ 58.5 = 0.1 mol and the molarity 0.1 ÷ 0.5 = 0.2 mol/L. It is used in chemistry labs, in pharmacy, in preparing solutions and in school and university assignments.
How to use
- Choose what you are looking for (molarity, mass, or volume)
- Enter the mass of the substance (g) or the moles
- Enter the molar mass (g/mol)
- Enter the volume of the solution (L or mL)
- See the molarity or the requested value
Frequently asked questions
What is molarity?
Molarity (M) = number of moles of solute / volume of solution in litres. E.g., 1 M NaCl = 58.44 g of NaCl dissolved in water up to 1 L of solution.
What is the difference between molarity and molality?
Molarity (M): mol/L of solution (depends on temperature because volume changes). Molality (m): mol/kg of solvent (does not depend on temperature). In dilute solutions, the values are almost the same.
How is dilution done?
Use M₁V₁ = M₂V₂. E.g., to make 500 mL of 0.1 M solution from a 1 M stock: V₁ = M₂V₂/M₁ = 0.1×500/1 = 50 mL stock + 450 mL water.
How many grams of NaCl are needed for 250 mL of 0.5 M solution?
m = M × MM × V = 0.5 × 58.44 × 0.25 ≈ 7.31 g. Choose "Mass" and enter MM = 58.44, molarity 0.5 and volume 0.25 L.