Molarity Calculator
The molar concentration of a solution: moles of solute per litre.
Result
Molarity (mol/L)
0.2500
How it works
Molarity is concentration by volume: moles of solute divided by litres of solution. A solution labelled 1 M contains one mole of dissolved substance in every litre. The denominator is the total solution volume, not the volume of solvent you started with. This matters in practice: dissolving the solute first and then topping up to the mark in a volumetric flask gives the right concentration, whereas adding solute to a litre of water gives slightly more than a litre and therefore a slightly weak solution. Because molarity is defined per litre, it shifts with temperature — liquids expand when warmed, so the same moles occupy more volume and the molarity falls. Molality, which uses kilograms of solvent instead, avoids that entirely, which is why precise physical chemistry prefers it while everyday lab work stays with molarity.
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Frequently asked questions
What does 1 M mean?
One mole of solute dissolved in one litre of solution.
Molarity vs molality?
Molarity uses litres of solution; molality uses kilograms of solvent and is temperature-independent.
How do I prepare a 1 M solution?
Weigh out one molar mass in grams — 58.44 g for NaCl — dissolve it in less than a litre of solvent, then top up to exactly the 1 L mark in a volumetric flask. Never add solute to a full litre.
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