Solve for:
Enter moles.
Enter volume.
Enter mass.
e.g. NaCl = 58.44, HCl = 36.46
Enter molar mass.
Enter volume.
Enter M1.
Enter V1.
Enter M2.
Molarity
—
💡
ℹ️ Molarity is temperature-dependent because liquid volume changes with temperature. For temperature-sensitive work, use molality instead of molarity.
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Sources & Methodology
Molarity definition and formula per IUPAC Green Book and standard general chemistry texts.
IUPAC Green Book — Quantities, Units and Symbols in Physical Chemistry, 3rd Ed.
Defines molarity (amount-of-substance concentration) as c = n/V. Symbol c, unit mol/L or mol/m3.
Zumdahl & Zumdahl — Chemistry, 10th Ed.
Standard undergraduate chemistry text covering solution concentration, dilution, and molarity calculations.
NIST — Atomic Weights and Isotopic Compositions
Standard atomic weights for molar mass calculations. nist.gov
Molarity: M = n / V(L)
Moles from mass: n = mass(g) / molar mass(g/mol)
Dilution: M₁V₁ = M₂V₂
mM = mmol/L = 0.001 mol/L
Moles from mass: n = mass(g) / molar mass(g/mol)
Dilution: M₁V₁ = M₂V₂
mM = mmol/L = 0.001 mol/L
M = n / V
Example: 0.5 mol NaCl in 250 mL (0.25 L).
M = 0.5 / 0.25 = 2.0 mol/L
From mass: 29.22 g NaCl / 58.44 g/mol = 0.5 mol → M = 0.5/0.25 = 2.0 M
M = 0.5 / 0.25 = 2.0 mol/L
From mass: 29.22 g NaCl / 58.44 g/mol = 0.5 mol → M = 0.5/0.25 = 2.0 M
Last reviewed: April 2026
How to Calculate Molarity
Molarity (M) is the most common way to express the concentration of a solution in chemistry. It tells you how many moles of solute are dissolved per liter of solution. The formula is simple: M = n/V, where n is moles of solute and V is the volume of solution in liters.
When you know the mass of a solute rather than moles, first convert using the molar mass: n = mass (g) / molar mass (g/mol). Then divide by the volume in liters to get molarity. This two-step process covers the vast majority of chemistry homework and lab preparation problems.
Common Molar Masses Reference
| Compound | Formula | Molar Mass (g/mol) |
|---|---|---|
| Sodium chloride | NaCl | 58.44 |
| Glucose | C₆H₁₂O₆ | 180.16 |
| Hydrochloric acid | HCl | 36.46 |
| Sodium hydroxide | NaOH | 40.00 |
| Sulfuric acid | H₂SO₄ | 98.08 |
| Acetic acid | CH₃COOH | 60.05 |
💡 Preparing a 1 M Solution Step-by-Step: 1. Calculate mass needed: mass = M × V(L) × molar mass. 2. Weigh the solute. 3. Dissolve in ~half the final volume. 4. Transfer quantitatively to a volumetric flask. 5. Bring to final volume mark with solvent. Never add all solvent first — always bring to volume after dissolving. For acids: always add acid to water, never water to acid.
Frequently Asked Questions
Molarity (M) = moles of solute / liters of solution. Unit: mol/L or M. Example: 2 mol dissolved in 0.5 L = 4 M solution.
M = n/V. Example: 0.5 mol NaCl in 250 mL (0.25 L): M = 0.5/0.25 = 2.0 M.
n = M × V(L). Example: 0.5 M solution, 2 L: n = 0.5 × 2 = 1.0 mol.
Step 1: n = mass(g) / molar mass(g/mol). Step 2: M = n/V(L). Example: 58.44 g NaCl in 1 L: n = 58.44/58.44 = 1 mol, M = 1/1 = 1.0 M.
Molarity = mol/L solution (changes with temperature). Molality = mol/kg solvent (constant with temperature). Use molality for colligative properties (boiling point elevation, freezing point depression).
Molarity = mol/L. Normality = equivalents/L. For acids: N = M × H+ ions. For bases: N = M × OH- ions. 1 M H2SO4 = 2 N H2SO4 (2 H+ per molecule).
A 1 M solution has 1 mol of solute per liter of solution total. For NaCl (58.44 g/mol): dissolve 58.44 g in enough water to make 1 L of solution (not just add 1 L of water).
1. Calculate mass: m = M × V × molar mass. 2. Weigh solute. 3. Dissolve in partial volume. 4. Transfer to volumetric flask. 5. Bring to volume mark. Never fill all solvent first.
M1V1 = M2V2. Example: dilute 100 mL of 6 M HCl to 2 M: V2 = M1V1/M2 = (6 × 0.1) / 2 = 0.3 L = 300 mL total.
mol/L, abbreviated M. Also: mM (millimolar) = mmol/L = 0.001 M. µM (micromolar) = µmol/L = 10⁻⁶ M. Clinical labs often use mM or µM.
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