Concentration Molarity Calculator
Molarity Calculator works out Molarity and Moles of solute from Moles of solute, Solute mass and Molar mass of the solute. The default figures on this page give molarity of 0.500000 mol/L; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
1 step
- M = n / V = 2 mol / 4 L = 0.5 mol/L
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
3 sources
What the Molarity Calculator calculates
Relates molarity, moles of solute, solute mass, molar mass and solution volume, solving for whichever of them the supplied values determine.
How to use this Molarity Calculator
Enter Moles of solute, Solute mass, Molar mass of the solute and Final solution volume. Molarity updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Molarity, Moles of solute and Solute mass.
The method follows OpenStax Chemistry 2e, section 3.3 Molarity, OpenStax Chemistry 2e, section 3.1 Formula Mass and the Mole Concept and IUPAC Compendium of Chemical Terminology (Gold Book), "amount concentration" and "mass concentration".
Research fixture R3369-GT-3: 2 mol in 4 L example
With Moles of solute: 2, Final solution volume: 4, the calculator returns Molarity: 0.5, Moles of solute: 2, Solution volume: 4. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Molarity, Moles of solute and Solute mass. The inputs you can vary are Moles of solute, Solute mass, Molar mass of the solute, Final solution volume, Target molarity and Answer wanted.
Understanding Molarity, Moles of solute and Solute mass
Solution preparation figures assume the final volume is made up to the stated value. Confirm reagent purity, hydration state and the molar mass you entered before weighing anything out.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to calculator molarity?
Relates molarity, moles of solute, solute mass, molar mass and solution volume, solving for whichever of them the supplied values determine. Open “How this is worked out” beside the result to see each step for your own figures.
What is the formula for calculating molarity?
Relates molarity, moles of solute, solute mass, molar mass and solution volume, solving for whichever of them the supplied values determine. On this page it is computed from Moles of solute, Solute mass and Molar mass of the solute and shown as Molarity, Moles of solute and Solute mass.
How do I convert mg/mL to molar?
It needs Moles of solute, Solute mass, Molar mass of the solute, Final solution volume, Target molarity and Answer wanted. Nothing else is required, and the figures stay in your browser.
Is molarity calculated in mL or l?
Relates molarity, moles of solute, solute mass, molar mass and solution volume, solving for whichever of them the supplied values determine. On the figures this page opens with — moles of solute 2 mol and final solution volume 4 L — the molarity is 0.5 mol/L. Put your own figures in their place and the working updates beside the result.
What information do I need for the Molarity Calculator?
You need Moles of solute, Solute mass, Molar mass of the solute, Final solution volume, Target molarity and Answer wanted. The page opens with default figures that give molarity of 0.500000 mol/L, so you can see the scale before entering your own.
What does this Molarity Calculator show?
It shows Molarity, Moles of solute, Solute mass, Mass concentration, Solution volume and Millimolar equivalent, with the working and any warnings for your entries.