Molarity Calculator
Convert mass, molar mass and volume into molarity, moles and millimolarity.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Enter solute mass in grams, molar mass in grams per mole, and solution volume in litres. Molarity is moles of solute per litre of solution; molar mass and volume must be positive.
Worked example
calculated with the default values below
Mass of solute 58.44 g · Molar mass 58.44 g/mol · Volume of solution 1 L Molarity 1.00000 M · Moles of solute 1.000000 mol · Millimoles 1,000.000 mmol · Millimolarity 1,000.000 mM · Concentration 58.4400 g/L · Volume needed for a 1 M solution 1.0000 L
Method and assumptions
Formula basis and scope
M = (mass / molar mass) / solution volume in litres.
Use final solution volume, not added solvent volume; assumes the entered solute molar mass is correct.
Data sources
Disclaimer
These calculators give general mathematical results. They suit study, planning and estimation — verify anything that feeds a graded submission, a published figure or a financial commitment.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
n = m ÷ M; c = n ÷ V
- n
- amount of substance, mol
- m
- solute mass, g
- M
- molar mass, g/mol
- c
- molarity, mol/L
- V
- solution volume, L
Moles = mass / molar mass; molarity = moles / solution volume. The volume required for a 1 M solution is undefined when the entered solute mass is zero.
Frequently asked questions
Why do the mass and molar mass both default to 58.44 grams?
The defaults are set to sodium chloride, whose molar mass is 58.44 g per mol, so entering 58.44 g of NaCl in 1 L yields exactly 1 M and 1 mol. The tool computes moles as mass divided by molar mass, then molarity as moles over volume, so swapping in a different solute means changing the molar mass field, water at 18.015 would give a completely different concentration for the same mass. The Volume needed for a 1 M solution output is simply mass divided by molar mass.