Molarity Calculator

Calculate solution molarity from solute mass, molar mass, and final solution volume for quick concentration preparation.

Calculate molarity

Enter mass in grams, molar mass in grams per mole, and final solution volume in milliliters.

Solute mass (g)

Molar mass (g/mol)

Solution volume (mL)

About molarity

Molarity describes the concentration of a solution as moles of solute per liter of final solution. It is commonly represented by M and reported in moles per liter. Because many chemical procedures specify how much substance is present in a given volume, molarity is one of the most frequently used concentration units in laboratory work, reaction planning, titration, and solution preparation. This calculator first converts solute mass to moles by dividing grams by the compound's molar mass in grams per mole. It then converts the entered solution volume from milliliters to liters and divides the mole amount by that volume. For example, 5.844 grams of sodium chloride at 58.44 grams per mole equals 0.1 mole. When the final solution volume is 500 milliliters, or 0.5 liter, the concentration is 0.2 mole per liter. Use the final volume of the entire solution, not merely the volume of solvent initially poured into the container. Dissolving a solid can change volume, so careful preparation normally means dissolving the solute in less than the desired volume and then adding solvent until a volumetric mark is reached. The molar mass must match the exact solute formula, including hydration state where relevant. Positive values and consistent listed units are required for a meaningful result. Unlike molality, molarity depends on volume and can therefore change with temperature as a solution expands or contracts. For routine work near a specified calibration temperature, the difference may be small, but high-precision applications should control and report temperature. The displayed result is rounded to at most six decimal places; input measurement uncertainty still determines the appropriate significant figures. This calculator handles the direct mass-to-molarity relationship and does not apply purity, dilution, dissociation, or reaction corrections. If a reagent is not pure, adjust the entered effective solute mass first. For dilutions from an existing stock solution, use the conservation relationship between initial concentration and volume and final concentration and volume instead.

Molarity examples

Inputs	Molarity	Context
5.844 g NaCl, 58.44 g/mol, 500 mL	0.2 mol/L	A sodium chloride solution
18.015 g, 18.015 g/mol, 1000 mL	1 mol/L	One mole in one liter
9.008 g, 180.16 g/mol, 250 mL	0.2 mol/L	A smaller glucose solution

How to calculate molarity

Enter the measured solute mass in grams.
Enter the solute molar mass in grams per mole.
Enter the final solution volume in milliliters.
Select Calculate molarity to view the concentration.

Molarity FAQ

Is solution volume the same as solvent volume?

Not necessarily, because dissolving a solute can change the total volume. Molarity uses the final volume of the complete solution.

How does temperature affect molarity?

Temperature can expand or contract a solution and therefore alter its volume. The mole amount remains constant, but the calculated concentration changes with that volume.

How do I account for reagent purity?

Multiply the measured sample mass by its purity fraction to find the effective solute mass. Enter that corrected mass rather than the full impure sample mass.

What is the difference between molarity and molality?

Molarity uses liters of final solution, while molality uses kilograms of solvent. Molarity is convenient for volumetric laboratory work, whereas molality is less affected by temperature.

Can I use millimoles and milliliters directly?

A ratio of millimoles per milliliter has the same numerical value as moles per liter. This calculator instead accepts grams and molar mass so it can perform the mole conversion for you.