Molarity Calculator
Find solution concentration in moles per liter from either moles or grams of solute.
Example
Dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in 1 L of water gives 1 mole in 1 liter, so the molarity is 1 M (1 mol/L).
How it works
Molarity (M) = moles of solute / volume in liters. In mass mode, moles = mass (g) / molar mass (g/mol), so M = mass / (molar mass x volume in L).
Good to know
This Molarity Calculator works out the concentration of a solution in moles per liter (M), the standard unit chemists use to describe how much solute is dissolved in a given volume. It offers two input paths: enter the moles of solute directly along with the volume, or enter the mass in grams plus the molar mass and let the tool convert mass to moles for you. It is aimed at chemistry students, lab technicians, and anyone preparing a solution who needs a quick, reliable concentration figure.
Reach for it when you are mixing a stock solution, scaling a recipe up or down, or checking homework where you know two of the three quantities (concentration, amount of solute, volume) and need the third. The mass mode is especially handy at the bench, since reagents are weighed in grams rather than counted in moles. The volume unit switch lets you type a beaker volume in milliliters without doing the divide-by-1000 step yourself.
Read the big number as moles of solute per liter of total solution. The two stats below it confirm the moles the tool used and the volume converted to liters, so you can sanity-check the inputs at a glance. Very small or very large results are shown in scientific notation, so a reading like 2.5e-4 M means 0.00025 mol/L. If the result is 0, check that volume is greater than zero, and in mass mode that the molar mass field is filled in.
One caveat worth remembering: molarity is defined per liter of finished solution, not per liter of solvent added. Dissolving solute usually changes the final volume, so for accurate work bring the solution up to the target volume in a volumetric flask after the solid dissolves rather than adding solute to a pre-measured liter of water.
Frequently asked questions
How do I convert milliliters to liters for molarity?
Divide the milliliter volume by 1000 to get liters (e.g. 250 mL = 0.25 L). This calculator does it automatically when you pick mL as the volume unit, since molarity is always defined per liter of solution.
What is the difference between molarity and molality?
Molarity (M) is moles of solute per liter of solution and depends on temperature because volume changes with heat. Molality is moles of solute per kilogram of solvent and is temperature-independent. This tool calculates molarity.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser. Your inputs never leave your device, and it works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
What is the formula for molarity?
Molarity equals moles of solute divided by the volume of solution in liters (M = mol / L). When you start from mass, first convert to moles by dividing the mass in grams by the molar mass in g/mol.
How do I find the molarity if I only know the grams of solute?
Divide the mass in grams by the molar mass in g/mol to get moles, then divide that by the volume in liters. The calculator's mass mode does both steps for you when you enter mass, molar mass, and volume.
What does a 1 M solution mean?
A 1 M (one molar) solution contains one mole of solute dissolved in enough solvent to make one liter of total solution. For example, 58.44 g of NaCl in 1 L of solution is 1 M.
How do I calculate the grams needed for a specific molarity?
Multiply the desired molarity by the volume in liters to get moles, then multiply by the molar mass to get grams. For instance, 0.5 M in 2 L of NaCl needs 0.5 x 2 x 58.44 = 58.44 g.
Where do I find the molar mass of a compound?
Add up the atomic masses of every atom in the chemical formula using values from the periodic table, or use a molecular weight calculator. The molar mass is expressed in grams per mole (g/mol).
Is molarity the same as concentration?
Molarity is one specific way of expressing concentration, measured in moles per liter. Other concentration units include molality (mol per kg of solvent), mass percent, and parts per million, which are calculated differently.
Why is my molarity calculation showing zero?
A result of zero usually means the volume is zero or blank, or in mass mode that the molar mass field is empty or zero, which makes the moles calculation undefined. Enter positive numbers in all required fields to get a value.
Does temperature affect molarity?
Yes, because liquids expand or contract with temperature, the volume of a solution changes, which slightly shifts its molarity. For temperature-independent measurements, chemists often use molality instead.
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