🧪 Molarity Calculator
Relate molarity, mass, volume, and molar mass. Pick what to solve for, enter the knowns — with the molar mass typed in or supplied by a chemical formula — and get the answer with units.
🧪 Result
Uses M = n/V with n = mass ÷ molar mass. For educational use — verify against authoritative sources and follow proper lab safety.
One relationship, three questions
M = n/V and n = mass ÷ molar mass are all you need to move between concentration, amount, and how much to weigh. Solving for molarity checks a solution you already made; solving for mass tells you what to weigh; solving for volume tells you how far a fixed amount of solute will go.
Reach for the Molar Mass Calculator when you need the g/mol, the Dilution Calculator to step a stock down to a working concentration, and the pH Calculator when the solute is a strong acid or base.
❓ Frequently Asked Questions
What is molarity and how is it calculated?
Molarity (M) is the amount of solute in moles divided by the volume of solution in litres: M = n / V. The number of moles comes from the mass and molar mass of the solute, n = mass ÷ molar mass. So to find molarity you need the solute's mass, its molar mass, and the final solution volume; the calculator combines these as M = (mass ÷ molar mass) ÷ volume.
How much of a solid do I weigh out for a target molarity?
Rearrange the same relationships: moles needed = molarity × volume, then mass = moles × molar mass. For example, 0.25 L of 2 M NaOH (molar mass 40 g/mol) needs 2 × 0.25 = 0.5 mol, which is 0.5 × 40 = 20 g. Choose 'Solve for: Mass' and the tool does this for you.
Can I use a chemical formula instead of typing the molar mass?
Yes. Switch 'Molar mass from' to 'Chemical formula' and enter something like NaCl or C6H12O6; the built-in molar-mass engine (the same one behind the Molar Mass Calculator) computes the g/mol for you using IUPAC standard atomic weights, then feeds it into the molarity relationship.
What units does it expect?
Mass in grams, molar mass in grams per mole, and volume in litres or millilitres (millilitres are converted to litres internally). Molarity is reported in mol/L, written M. Make sure your solute mass and molar mass refer to the same substance, and that the volume is the total solution volume, not just the solvent added.
Is this suitable for lab preparation?
It is a planning and teaching aid. Real preparations should account for hydrate water, purity/assay of the reagent, and volumetric technique (dissolve, then make up to volume). For educational use — verify against authoritative sources and follow proper lab safety.