Molarity Calculator
Calculate solution molarity (moles per liter) from solute mass, molar mass and solution volume.
How to use the Molarity Calculator
- Enter your inputs into the Molarity Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The molarity formula
M = (mass / molar mass) / volume = mol / L
M is molarity in mol/L. Convert solute mass to moles by dividing by the substance's molar mass (g/mol), then divide by the solution's volume in liters.
Worked example
Dissolving 5.85 g of NaCl (molar mass 58.44 g/mol) in 250 mL of water: moles = 5.85/58.44 ≈ 0.100 mol; volume = 0.250 L; M = 0.100/0.250 = 0.400 mol/L.
Frequently asked questions
What's the difference between molarity, molality and normality?
Molarity (M): mol solute / L solution. Molality (m): mol solute / kg solvent. Normality (N): equivalents / L (depends on reaction). Molarity is most common in lab work.
How do I prepare a specific molarity?
Calculate mass needed: mass = molarity × volume × molar mass. Dissolve in a smaller volume of solvent, then dilute to the final volume in a volumetric flask.
Does temperature affect molarity?
Yes — solutions expand or contract with temperature, changing the volume and thus the molarity. Standard practice: prepare and report molarity at a specified temperature (typically 25°C).