Calculate molar concentration of solutions in mol/L (M)
Chemical Calculator
Molarity — Quick answer
Molarity (M) is the amount of solute (in moles) per litre of solution. It is the most common concentration unit in chemistry and the basis for the dilution equation C1V1 = C2V2.
M = n / V | n = m / MW | C1V1 = C2V2
M — molarity (mol/L)
n — moles of solute
V — volume of solution in litres
m — mass of solute (g)
MW — molar mass (g/mol)
C, V (1/2) — concentration and volume before / after dilution
Worked example: Prepare 250 mL of 0.10 M NaCl. MW(NaCl) = 58.44 g/mol. Mass = M × V × MW = 0.10 × 0.250 × 58.44 = 1.46 g. Dilute to 250 mL with deionised water. To make 100 mL of 0.020 M from this stock: V1 = (0.020 × 100) / 0.10 = 20 mL stock + 80 mL water.
Common laboratory stock concentrations
Reagent
Stock (M)
Typical working (M)
HCl (37% w/w)
12.1
0.1 – 1.0
H2SO4 (98% w/w)
18.0
0.1 – 1.0
NaOH pellets
10.0 (from solid)
0.1 – 1.0
NH4OH (28% w/w)
14.8
0.1 – 1.0
Acetic acid (glacial)
17.4
0.1 – 1.0
Standard / source: IUPAC Green Book Section 2.10 (Chemical thermodynamics).
This calculator uses the standard molarity calculator formula:
Molarity Formula
M = n / V (mol/L)
Frequently Asked Questions
What is molarity?⌄
Molarity (M) is the number of moles of solute dissolved per litre of solution: M = n ÷ V. It is the most common way to express solution concentration.
What is the molarity of 5.85 g of NaCl in 500 mL?⌄
NaCl molar mass = 58.44 g/mol. Moles = 5.85 ÷ 58.44 = 0.1001 mol. Molarity = 0.1001 ÷ 0.5 L = 0.200 mol/L (0.2 M).
What is the difference between molarity and molality?⌄
Molarity (M) = moles per litre of solution. Molality (m) = moles per kilogram of solvent. Molality is temperature-independent; molarity is not.
How do I prepare a 1 M solution?⌄
Weigh out 1 mole of solute (mass = molar mass in grams), dissolve it in solvent, and transfer to a 1-litre volumetric flask. Fill to the 1-litre mark with solvent.
What is normality vs molarity?⌄
Normality (N) = Molarity × number of equivalents (n-factor). For HCl, n=1 so 1 M = 1 N. For H₂SO₄, n=2 so 1 M = 2 N.
How does temperature affect molarity?⌄
Temperature changes the volume of the solution, which changes molarity. A solution heated up becomes less concentrated as the volume expands.
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Definition of molar concentration. Atomic weights per the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW, 2021).
Core formula
M = moles / litres of SOLUTION · moles = mass / molar mass · C₁V₁ = C₂V₂
Why this matters
Molarity is per litre of solution, not of solvent — you dissolve then make up to volume, you do not add solute to a litre of water. Molarity is also temperature-dependent (volume expands); molality is not.
Independently verified
12 July 2026 — Re-derived from the governing standard and checked numerically against worked reference cases from the standard itself — not merely tested for “returns a number”.
Results are for guidance. Verify against the current edition of the governing standard and have a qualified professional review before use in practice.