Titration Calculator
For a strong acid titrated with a strong base, enter the volumes and known concentration to find the unknown value at the equivalence point.
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Formula
At the equivalence point of a strong acid with a strong base:
acid conc × acid volume × H+ per acid = base conc × base volume × OH- per base
Volumes in mL with concentrations in mol/L give mmol. The pH at equivalence is 7.00 at 25 C.
Worked example
25 mL of HCl needs 22.5 mL of 0.100 M NaOH. Acid concentration = 0.100 × 22.5 / 25 = 0.0900 mol/L, with 2.25 mmol neutralised and a total volume of 47.5 mL.
Assumptions
Strong acid and strong base only, 25 C, complete dissociation.
Frequently asked questions
How do you calculate the unknown concentration in a titration?
At equivalence, moles of H+ equal moles of OH-: acid concentration × acid volume × H+ per acid = base concentration × base volume × OH- per base. For 25 mL of HCl needing 22.5 mL of 0.100 M NaOH, acid = 0.100 × 22.5 / 25 = 0.0900 mol/L.
What if the acid or base has more than one H+ or OH-?
Include it in the ratio. A 20 mL sample of a diprotic acid needing 30 mL of 0.2 M NaOH has 6 mmol OH- neutralised, so acid = 6 / (2 × 20) = 0.15 mol/L.
What is the pH at the equivalence point?
For a strong acid with a strong base the salt is neutral, so the pH at equivalence is 7.00 at 25 C. Weak acids or bases give a different value, which this calculator does not cover.
Can I use mL directly?
Yes. Concentration in mol/L times volume in mL gives mmol, and the same unit appears on both sides, so no conversion is needed. The equivalence volume of 0.2 M base for 25 mL of 0.1 M HCl is 25 × 0.1 / 0.2 = 12.5 mL.