About the Molarity Calculator
Molarity is the number of moles of a substance dissolved in each litre of solution, written mol/L or M. This molarity calculator covers the four jobs people do most in the lab: finding the molarity of a solution from the mass of solute and the volume, working out how many grams to weigh for a target molarity, finding the volume that a given mass will make at a chosen molarity, and planning a dilution from a stock solution using C1V1 equals C2V2. It shows the moles involved and gives volumes in millilitres when they are small.
Updated October 2026
How to use the Molarity Calculator
- 1Pick what you want to find: molarity, mass, volume or a dilution.
- 2Enter the molar mass of the solute in g/mol if the job needs it.
- 3Fill in the other values the tool asks for, using litres and grams.
- 4Read the answer, plus the moles and any related figures.
- 5For a dilution, add solvent to the stock until you reach the final volume.
A worked example
Say you need 100 mL of 0.2 M glucose. The molar mass of glucose is 180.16 g/mol. Convert 100 mL to 0.1 L. The mass you need is 0.2 times 0.1 times 180.16, which equals 3.603 grams. Weigh that out, dissolve it in about 80 mL of water, then add water until the solution reaches the 100 mL mark. The calculator does the same sums and shows the mass, the moles and the result in milligrams.
Laboratory tips
- Use a volumetric flask for accurate final volumes, not a beaker.
- Always add concentrated acid to water, never water to acid.
- Check whether your solid is a hydrate, because the water of crystallisation changes the molar mass.
- Correct for purity if the label says the chemical is not 100% pure.
- Label every solution with its name, concentration and date.
Related chemistry tools
Use the Molecular Weight Calculator to find molar mass from a formula, the Density Calculator for mass and volume of liquids and the Percentage Calculator for percent-by-weight solutions. The Unit Converter converts litres and millilitres. This tool gives study and bench guidance, and you should follow your own lab's safety procedures and methods.
Features
- Molarity from mass, molar mass and volume
- Grams to weigh for a target molarity
- Volume of solution a given mass will make
- Dilution volumes using C1V1 = C2V2
- Moles and millimolar shown too
- Small volumes displayed in mL
- Runs in your browser
Frequently asked questions
How do you calculate molarity?
Divide the number of moles of solute by the volume of solution in litres. Moles are the mass in grams divided by the molar mass. So 5.844 grams of sodium chloride (molar mass 58.44) is 0.1 mole, and dissolved to make 1 litre it gives a 0.1 molar solution.
How do I make a solution of a certain molarity?
Multiply the molarity by the final volume in litres and by the molar mass to get the grams to weigh. To make 250 mL of 0.5 M sodium chloride, you need 0.5 times 0.25 times 58.44, which is 7.305 grams. Dissolve in less water, then top up to the final volume in a volumetric flask.
What is the C1V1 = C2V2 dilution formula?
When you dilute a solution, the amount of solute stays the same, so concentration times volume is equal before and after. If you have a 12 M stock and want 0.5 litres at 1 M, you need 1 times 0.5 divided by 12, which is about 41.7 mL of stock, then add solvent up to 500 mL.
Where do I find the molar mass?
Add up the atomic weights of every atom in the formula. Sodium chloride is 22.99 plus 35.45, which is 58.44 g/mol. You can use the Molecular Weight Calculator on this site to get it for any formula.
What is the difference between molarity and molality?
Molarity is moles per litre of solution, so it changes a little with temperature as the volume changes. Molality is moles per kilogram of solvent and does not change with temperature. This tool works with molarity.
Is the volume the solvent volume or the final volume?
It is the final volume of the finished solution. When you dissolve a solid, the total volume is usually a little different from the volume of water you started with, which is why recipes tell you to dissolve and then make up to the mark.