Molarity Calculator
Calculate molarity (M), mass, volume, or moles of a solution. Enter any three values to find the fourth. Formula: M = mass ÷ (molar mass × volume).
Common Molar Masses
Quick reference for frequently-used compounds. Values in g/mol (from IUPAC 2021 atomic weights). "Molar mass" is the IUPAC-preferred term; "molecular weight" is an older informal synonym.
| Compound | Formula | Molar mass (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Sodium chloride | NaCl | 58.44 |
| Sodium hydroxide | NaOH | 40.00 |
| Hydrochloric acid | HCl | 36.46 |
| Sulfuric acid | H₂SO₄ | 98.08 |
| Nitric acid | HNO₃ | 63.01 |
| Glucose | C₆H₁₂O₆ | 180.16 |
| Sucrose | C₁₂H₂₂O₁₁ | 342.30 |
| Ethanol | C₂H₅OH | 46.07 |
| Acetic acid | CH₃COOH | 60.05 |
| Calcium carbonate | CaCO₃ | 100.09 |
| Potassium permanganate | KMnO₄ | 158.03 |
| Potassium chloride | KCl | 74.55 |
| Ammonium chloride | NH₄Cl | 53.49 |
How to Calculate Molarity
- Measure the mass of solute in grams.
- Find the molar mass (M) of the solute in g/mol. For common compounds, see the table above. "Molar mass" is the IUPAC term; "molecular weight" (Mr) is the older informal name and is strictly dimensionless.
- Calculate moles: n = mass ÷ molar mass
- Measure the volume of the total solution in liters.
- Apply the molarity formula: M = n ÷ V
Example: Dissolve 5.84 g of NaCl (molar mass = 58.44 g/mol) in water to make 0.5 L of solution.
n = 5.84 ÷ 58.44 = 0.1 mol
M = 0.1 ÷ 0.5 = 0.2 mol/L (0.2 M)
Molarity Formulas
The four rearrangements of the molarity equation, one per calculation mode. Below, M (italic) is molar mass in g/mol and V is volume in L:
- Find Molarity: Molarity = mass ÷ (M × V)
- Find Mass: mass = Molarity × M × V
- Find Volume: V = mass ÷ (Molarity × M)
- Find Moles: n = Molarity × V
Frequently Asked Questions
What is molarity?
Molarity (M) measures concentration as moles of solute per liter of solution. A 1 M solution contains 1 mole of solute in 1 liter of total solution. Also called molar concentration, it is the most common concentration unit in chemistry.
How do you calculate molarity?
Formula: Molarity = mass ÷ (molar mass × volume)
Example: 5.84 g NaCl (molar mass 58.44 g/mol) in 0.5 L → M = 5.84 ÷ (58.44 × 0.5) = 0.2 M.
What is the difference between molarity and molality?
Molarity (M) = moles per liter of solution — volume-based and temperature-dependent (volume changes with temperature).
Molality (m) = moles per kilogram of solvent — mass-based and temperature-independent.
For dilute aqueous solutions near room temperature, molarity and molality are approximately equal.
What units is molarity measured in?
Molarity is measured in mol/L, abbreviated M (molar). Common sub-units:
- mM (millimolar) = 10⁻³ M
- µM (micromolar) = 10⁻⁶ M
- nM (nanomolar) = 10⁻⁹ M
How do I convert grams to moles?
Formula: moles = mass (g) ÷ molar mass (g/mol)
Example: 10 g NaCl ÷ 58.44 g/mol = 0.171 mol. The molar mass is the sum of the atomic masses of all atoms in one molecule (or formula unit) of the substance, expressed in g/mol. "Molar mass" is the IUPAC term; "molecular weight" is the older informal synonym.
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All calculations on CoolConversion use formulas and constants documented by internationally recognised standards bodies (such as IUPAC and NIST).
