Molarity Calculator

What molarity tells you

Molarity is the most commonly used concentration unit in chemistry. It tells you how many moles of solute are dissolved in each liter of solution, written as M (e.g., “2 M HCl” means 2 moles of hydrochloric acid per liter). It’s essential for preparing solutions, performing titrations, and doing any reaction calculation in solution.

A frequent mistake is using solvent volume instead of total solution volume. Molarity is defined relative to the final volume of the entire solution after the solute has been dissolved, not the volume of water you started with.

How to Calculate Molarity (step by step)

Step One: Calculate moles of solute

Divide the mass of your solute by its molar mass.

moles = mass of solute (g) ÷ molar mass (g/mol)

For 58.44 g of NaCl (molar mass 58.44 g/mol): 58.44 ÷ 58.44 = 1.000 mol.

Step Two: Divide by solution volume in liters

Divide the moles by the total volume of the prepared solution.

molarity = moles ÷ volume of solution (L)

For 1.000 mol in 1 L of solution: 1.000 ÷ 1 = 1.000 M.

Common uses

Preparing lab solutions of a specific concentration, calculating reagent amounts for reactions, dilution calculations (M₁V₁ = M₂V₂), and interpreting titration results.

About the formula: Molarity (M) = Moles of solute ÷ Volume of solution (L). Moles = Mass (g) ÷ Molar mass (g/mol).

Frequently Asked Questions

What is molarity?+

Molarity (M) is the number of moles of solute dissolved per liter of total solution. A 1 M NaCl solution contains 1 mole (58.44 g) of NaCl in every liter of solution.

Is the volume the amount of solvent or solution?+

It's the total volume of the final solution, not the volume of solvent alone. When you dissolve a solute in water and top up to 1 L total, that 1 L is your solution volume.

How do I dilute a solution to a target molarity?+

Use M₁V₁ = M₂V₂. Multiply your current molarity by the volume you have, then divide by the target molarity to get the final volume you need to dilute to.