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Molarity, Normality & Dilution Calculator
Work out how many grams to weigh for any molar or normal solution, find the concentration of a solution you made, dilute a stock with C₁V₁ = C₂V₂, prepare dilute acids from concentrated bottles, and convert % w/v and ppm. Free, no sign-in, works on your phone.
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How it works
Normality (N) = Molarity (M) × n-factor
C₁ × V₁ = C₂ × V₂
Stock molarity = (Assay % ÷ 100) × Density (g/mL) × 1000 ÷ Molecular weight
The n-factor is the number of reacting units per molecule: H⁺ ions for an acid, OH⁻ for a base, or electrons gained or lost in a redox reaction.
Worked examples
0.1 M sodium chloride, 1000 mL
Mass = 0.1 × 1 × 58.44 = 5.844 g NaCl. Dissolve and make up to 1000 mL in a volumetric flask.
0.1 N sulphuric acid, 1000 mL, from 98% acid
Stock = 0.98 × 1.84 × 1000 ÷ 98.08 = 18.38 M. H₂SO₄ has n-factor 2, so 0.1 N = 0.05 M. Volume = 0.05 × 1000 ÷ 18.38 = 2.72 mL of concentrated acid, added slowly to water and made up to 1000 mL.
Dilute 1 M stock to 0.1 M, 100 mL
V₁ = 0.1 × 100 ÷ 1 = 10 mL of stock, made up to 100 mL (add 90 mL diluent). Dilution factor 1 in 10.
Common mistakes
- Hydrate vs anhydrous salt: CuSO₄·5H₂O (249.68 g/mol) and anhydrous CuSO₄ (159.60 g/mol) need very different weights. Use the formula on your bottle.
- Normality of di- and tri-basic acids: 1 M H₂SO₄ is 2 N; 1 M H₃PO₄ is 3 N.
- Adding water to acid: always add concentrated acid slowly to water, with cooling.
- Using a beaker for volume: make up to the mark in a volumetric flask for accurate strength.
- Volumetric solutions: a calculated strength is nominal. Standardise against a primary standard to get the actual factor.
Verified against the Indian Pharmacopoeia’s worked examples
Checked against the Indian Pharmacopoeia Commission’s guidance document on calculations (IPC/GD/10, Calculations in IP).
| Calculation | Reference answer | LabKit result |
|---|---|---|
| 0.1 M sodium hydroxide, 500 mL | 2.0 g | 2.000 g |
| 1 N sulphuric acid, 1000 mL | 49.0 g | 49.04 g |
This check is our own; it is not an endorsement by the Indian Pharmacopoeia Commission.
Frequently asked questions
What is the difference between molarity and normality?
Molarity is moles of solute per litre. Normality is gram-equivalents per litre, which is molarity multiplied by the n-factor. For HCl and NaOH they are the same; for H₂SO₄ normality is twice the molarity.
How do I find the n-factor?
For acids it is the number of replaceable H⁺ (HCl 1, H₂SO₄ 2, H₃PO₄ 3). For bases it is the number of OH⁻ (NaOH 1, Ca(OH)₂ 2). For oxidising agents it is the electrons gained per molecule, e.g. KMnO₄ is 5 in acid medium and K₂Cr₂O₇ is 6.
Is 1 ppm the same as 1 mg/L?
For dilute water-based solutions, yes: 1 ppm ≈ 1 mg/L and 1 ppb ≈ 1 µg/L, because 1 L of water weighs about 1 kg.
Why do the acid values say “typical”?
Concentrated acids are sold at slightly different strengths. The assay % and density are printed on the label or certificate of analysis; enter those values for the most accurate answer.
Is molarity the same as molality?
No. Molarity is per litre of solution; molality is per kilogram of solvent. This calculator uses molarity, which is what volumetric flasks give you.
Related calculators
Results are for guidance. Check calculations and standardise volumetric solutions before use in GMP or regulated records.