What is the molarity formula?

Molarity (M) equals the amount of solute in moles (n) divided by the volume of solution in litres (V), so M = n / V. Because moles equal mass divided by molar mass, this expands to M = mass / (Mr times V) when you start from grams.

How do I convert grams to moles?

Divide the mass in grams by the molar mass in grams per mole: moles = mass / Mr. For example, 29.22 g of NaCl (Mr = 58.44 g/mol) is 29.22 / 58.44 = 0.5 mol. This calculator does the conversion for you, deriving Mr from a formula or a value you type.

How much solute do I need for a given molarity?

Set the dropdown to "Mass of solute to weigh out". Mass = molarity times molar mass times volume in litres. For 1 L of 0.5 M NaCl that is 0.5 times 58.44 times 1 = 29.22 g.

What is the difference between molarity and molality?

Molarity is moles of solute per litre of solution (volume-based, so it shifts slightly with temperature as the solution expands or contracts). Molality is moles of solute per kilogram of solvent (mass-based, temperature-independent). This tool calculates molarity.

How do I prepare a diluted solution from a stock?

Use the relationship C1·V1 = C2·V2: the moles of solute are conserved on dilution. Work out the moles you need with this calculator, then see the dedicated dilution calculator to find the stock volume to pipette and the water to add.

Is my data sent anywhere?

No. Every calculation runs locally in your browser using JavaScript, and no figures are ever uploaded or stored on a server.

Molarity Calculator — Gera Tools

Molarity (symbol M, units mol/L, also written mol·dm⁻³) is the amount of solute dissolved per litre of solution. It is the workhorse concentration unit in chemistry: titrations, reaction stoichiometry, buffer preparation and dilutions are all set up in molarity. This calculator solves the molarity relationship for any one of four quantities — the concentration itself, the amount of solute in moles, the mass to weigh out, or the volume of solution to make up — and it bridges grams and moles for you through the molar mass, so you can go straight from a balance reading to a concentration without a separate step.

How it works

The single relationship behind every mode is:

M = n / V

where n is the amount of solute in moles and V is the volume of solution in litres. Amount of substance connects to a mass on the balance through the molar mass Mr (g/mol):

n = mass / Mr, so M = mass / (Mr · V)

Choose what to solve for and the tool rearranges the equation, then shows the rearranged form filled in with your numbers:

Molarity = mass ÷ (Mr × V), or n ÷ V if you enter moles directly
Moles = M × V
Mass = M × V × Mr
Volume = n ÷ M

You can supply the molar mass two ways. Type a chemical formula — NaCl, Ca(OH)2, KMnO4, even hydrates like CuSO4(H2O)5 — and a recursive-descent parser totals the standard atomic weights (IUPAC 2021 conventional values) to give Mr. Or switch to manual entry and type a molar mass directly. Volumes accept litres, millilitres or microlitres; masses accept grams or milligrams; amounts accept moles or millimoles, all converted internally to a consistent base before the arithmetic runs.

Worked example

You need 250 mL of a 0.100 M sodium chloride solution. NaCl has a molar mass of 58.44 g/mol.

Convert the volume to litres: V = 250 mL ÷ 1000 = 0.250 L
Find the moles required: n = M × V = 0.100 mol/L × 0.250 L = 0.0250 mol
Convert moles to a mass to weigh out: mass = n × Mr = 0.0250 mol × 58.44 g/mol = 1.461 g

Weigh 1.461 g of NaCl, dissolve it in a little water, then make the solution up to exactly 250 mL in a volumetric flask. Working the same example backwards: if you actually dissolved 1.461 g in 250 mL, the molarity is 1.461 ÷ (58.44 × 0.250) = 0.100 mol/L, confirming the result.

Solve for	Rearranged formula
Molarity	mass ÷ (Mr × V)
Moles	M × V
Mass	M × V × Mr
Volume	n ÷ M

A quick reference: a 1 M solution holds one mole of solute per litre. For NaCl that is 58.44 g made up to 1 L; for glucose (Mr ≈ 180.16 g/mol) it is about 180.16 g per litre. Every figure here is computed in your browser and nothing is uploaded or stored.