Normality formula
Normality (N) is gram equivalents of solute ÷ litres of solution. An equivalent accounts for how many reactive units (H+, OH− or electrons) each formula unit provides, so normality equals molarity multiplied by the n-factor. It is widely used in acid–base and redox titrations. For mass-based concentration, compare with the molality calculator.
How to use this calculator
Enter the number of gram equivalents of solute and the total solution volume in litres. If you have millilitres, divide by 1000 first. The calculator divides equivalents by litres to return normality in eq/L, and rejects a zero volume.
To get equivalents from moles, multiply by the n-factor: 1 mole of sulfuric acid supplies 2 equivalents, while 1 mole of hydrochloric acid supplies 1. Note that the denominator is the total volume of the finished solution, not the volume of solvent you started with. Normality is molarity multiplied by the number of reactive equivalents, so start from the molarity calculator.
Worked example
A solution contains 0.5 equivalents of acid in 2 L. Normality = 0.5 ÷ 2 = 0.25 N. For a monoprotic acid this equals 0.25 M, but for sulfuric acid (2 equivalents per mole) the molarity would be half the normality.
The point of working in equivalents is that titration arithmetic becomes a single line: N1 × V1 = N2 × V2 at the endpoint, with no stoichiometric ratio to track. The trade-off is that normality is reaction-specific, which is why modern practice often prefers molarity and an explicit balanced equation. For strong acids and bases the equivalent concentration feeds directly into the pH calculator.
Frequently asked questions
- What is normality?
- Normality is the number of gram equivalents of solute per litre of solution, written with the symbol N and units eq/L.
- How is normality related to molarity?
- Normality equals molarity times the n-factor (the number of equivalents per mole), so for a monoprotic acid the two are equal.
- What is an equivalent?
- An equivalent is the amount of a substance that supplies one mole of reactive units, such as one mole of H+ in an acid or one mole of electrons in a redox reaction.
- When is normality used?
- It is most useful in titration calculations, where equivalents of acid and base (or oxidant and reductant) react in a one-to-one ratio.
- Can one solution have more than one normality?
- Yes, because the n-factor depends on the reaction. The same potassium permanganate solution has a different normality in acidic conditions than in neutral ones, so a normality figure should always be quoted alongside the reaction it applies to.