Chemistry & Lab tools

Molarity calculator

Set a target molarity and volume, and get the exact mass of solute to weigh out — no manual moles conversion required.

Formula

Mass = Molarity × Volume (L) × Molar Mass

Target solution

Target molarity

Desired concentration of the final solution

mol/L

Volume of solution

Total volume you want to prepare

Molar mass of solute

g/mol, from the label or periodic table

g/mol

Mass of solute needed

0 g

Moles required–

Concentration–

Mass vs. molarity at this volume

Dissolve the calculated mass in a portion of solvent first, then top up to the final volume mark in a volumetric flask — adding solvent to a fixed mass changes the final volume slightly less predictably than diluting up to a calibrated line. Always confirm molar mass against the specific salt form you’re using, since hydrates carry extra mass from water of crystallisation.

Frequently asked questions

What is molarity?

A measure of concentration expressed as moles of solute per litre of solution, written as mol/L or M — one of the most common ways to express solution strength in chemistry.

How do I calculate mass needed for a target molarity?

Multiply target molarity by volume in litres to get moles needed, then multiply moles by molar mass to get the mass in grams required.

Where do I find the molar mass of a compound?

It’s the sum of atomic masses of every atom in the formula, found on the periodic table, and usually printed on the reagent bottle or safety data sheet as g/mol.

Is this molarity calculator free to use?

Yes. It runs entirely in your browser, needs no account, and nothing you enter is stored or transmitted.