What Is Molar Concentration?

Molar concentration — or molarity (M) — expresses how much solute is dissolved in a given volume of solution: M = moles of solute ÷ liters of solution. It is the chemist's standard measure of concentration because moles, unlike mass, relate directly to the number of particles participating in a reaction. A 1 M solution contains one mole of solute per liter.

How This Calculator Works

Enter the mass of your solute, its molar mass, and the final volume of the solution. The calculator first converts mass to moles — moles = mass ÷ molar mass — then divides by volume to get molarity. It also reports grams per liter and millimolar for convenience, and plots how concentration falls as the solution is diluted.

The default example dissolves 58.44 g of NaCl (molar mass 58.44 g/mol) in 1.0 L of water. That is exactly one mole of salt, so the result is precisely 1.000 M — a clean anchor for understanding the units before you enter your own values.

Using Molarity in the Lab

To prepare a solution of a target molarity, weigh out the mass = M × molar mass × volume, dissolve it in less solvent than the final volume, and then top up to the mark. Remember that volume is the total solution volume, not the solvent added. For dilutions, the amount of solute is conserved, so C₁V₁ = C₂V₂ holds exactly.

Common Applications

Molarity drives stoichiometry — reaction quantities are measured in moles, and molarity converts volume to moles. Biologists prepare buffers and media at specific millimolar concentrations, pharmacists formulate doses, and environmental labs report pollutant levels in molar terms. Getting the concentration right is the difference between a working reaction and a wasted batch.