Molarity Calculator

Molarity — the number of moles of a substance dissolved per liter of solution — is a standard way to express chemical concentration in labs and chemistry courses. Enter any two of mass, volume, and concentration along with the compound's molecular weight into the Molarity Calculator to solve for the missing third value. Secondary outputs include moles of solute and the formula used, with unit support ranging from nanoliters to liters and femtomolar to molar.

Mass of the solute. Leave blank to calculate this value.

g/mol

Formula weight of the compound in grams per mole (e.g. NaCl = 58.44 g/mol).

Volume of the solution. Leave blank to calculate this value.

Molar concentration of the solution. Leave blank to calculate this value.

Results

Calculated Result

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Result Parameter

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Moles of Solute

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Formula Used

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Frequently Asked Questions

What is molarity and how is it defined?

Molarity (M), also called molar concentration, is the number of moles of solute dissolved per liter of solution. It is expressed in units of mol/L (or simply M). For example, a 1 M NaCl solution contains 1 mole of sodium chloride in every liter of solution.

What is the molarity calculator equation?

The core equation is: Concentration (mol/L) = Mass (g) ÷ [Molecular Weight (g/mol) × Volume (L)]. Rearranging this gives you Mass = Concentration × Molecular Weight × Volume, or Volume = Mass ÷ (Concentration × Molecular Weight). Enter any three known values to solve for the fourth.

What is molecular weight (formula weight)?

Molecular weight (also called formula weight) is the sum of the atomic weights of all atoms in a compound's chemical formula, expressed in grams per mole (g/mol). For example, NaCl has a molecular weight of 58.44 g/mol (sodium: 22.99 + chlorine: 35.45). You can find this value on the compound's data sheet or safety data sheet.

What is the mass of compound needed to make a required solution?

To find the required mass, use the formula: Mass (g) = Concentration (mol/L) × Volume (L) × Molecular Weight (g/mol). For instance, to prepare 500 mL of a 0.1 M NaCl solution, you need 0.1 × 0.5 × 58.44 = 2.922 g of NaCl.

How much solvent is needed to dissolve a compound for a required solution?

To calculate the required volume, rearrange the molarity equation: Volume (L) = Mass (g) ÷ [Concentration (mol/L) × Molecular Weight (g/mol)]. Enter your known mass, molecular weight, and target concentration into the calculator, and leave the volume field blank to solve for it.

How do I calculate molarity from a known mass and volume?

Divide the mass (in grams) by the product of the molecular weight (g/mol) and the volume (in liters). The result is the molar concentration in mol/L. In this calculator, enter your mass, molecular weight, and volume — leave concentration blank — to get the answer automatically.

Which field should I leave blank to calculate that value?

Leave exactly one field blank — either mass, volume, or concentration — and fill in the other two along with the molecular weight. The calculator detects which field is missing and solves for it. If more than one field is blank, the calculator will prompt you to provide more information.

Does it matter which unit I select for mass, volume, or concentration?

No — the calculator automatically converts all units to base SI values before computing. You can freely mix milligrams with millimolar or micrograms with nanomolar, and the result will be correctly converted back into your chosen output unit.