Titration Calculator

What a Titration Calculator Actually Solves

Titration is a lab technique that finds an unknown concentration by slowly adding a solution of known concentration, the titrant, until the reaction reaches its endpoint. Omni Calculator's titration tool frames the core relationship simply: at the equivalence point, the moles of titrant added exactly match the moles of analyte present, according to the reaction's stoichiometry. This calculator covers the two calculations that come directly out of that relationship, working backward from titration data to an unknown concentration, and working out what the pH actually is at that equivalence point, which for a weak acid or weak base titration is not the 7 many people expect.

Finding an Unknown Concentration from Titration Data

The core equation is M_aV_a × n_a = M_bV_b × n_b, rearranged to solve for the unknown analyte concentration once you know the titrant's molarity, the volume of titrant used to reach the endpoint, and the analyte's volume. This exact question, working out an unknown acid's concentration from how much base it took to neutralize it, comes up constantly, a frequently asked Quora question on titrating an unknown acid with a strong base walks through the identical logic this calculator's first tab automates.

The Stoichiometric Mole Ratio Matters

A simple 1:1 mole ratio only applies to monoprotic acid and monobasic base pairs, sulfuric acid reacting with sodium hydroxide needs two moles of base per mole of acid, and the calculation shifts accordingly. University of Calgary's titration calculations chapter walks through exactly this kind of polyprotic case, where skipping the stoichiometric coefficient in the calculation is one of the most common sources of an incorrect concentration result. Our calculator's mole ratio field lets you enter that coefficient directly rather than assuming a 1:1 reaction by default.

pH at the Equivalence Point Isn't Always 7

The equivalence point is only neutral, pH 7, when a strong acid reacts with a strong base. Titrations.info's equivalence point calculation guide explains why weak acid and weak base titrations shift away from 7: the product left behind at equivalence is a salt whose ion hydrolyzes water, a weak acid's conjugate base makes the solution basic, a weak base's conjugate acid makes it acidic. This calculator's second tab computes that actual equivalence point pH from the weak acid's pKa or weak base's pKb rather than assuming neutral by default.

Weak Base Titrated with Strong Acid: An Acidic Equivalence Point

When a weak base like ammonia is titrated with a strong acid, the equivalence point contains only the conjugate acid, NH4+, which hydrolyzes water and produces a mildly acidic solution rather than a neutral one. LibreTexts' walkthrough of titrating a weak base with a strong acid uses the conjugate acid's Ka, derived from the weak base's Kb via Ka × Kb = Kw, to compute the resulting [H+] and pH, exactly the calculation our weak-base mode runs. If you specifically need the pH partway through a titration, at the half-equivalence point where pH equals pKa, our Buffer pH Calculator handles that Henderson-Hasselbalch relationship directly.

Choosing an Indicator

An indicator needs to change color right around the equivalence point pH, not at pH 7 by default, choosing phenolphthalein for an acidic-equivalence titration would give a false, premature endpoint reading. MiniWebTool's titration calculator pairs its equivalence point pH output with a recommended indicator for exactly this reason, our calculator does the same, suggesting methyl orange for an acidic equivalence point, bromothymol blue near neutral, and phenolphthalein for a basic equivalence point. If you need to work out the volume of base required to fully neutralize a given acid rather than the resulting equivalence point pH, our Neutralization Calculator handles that volume calculation directly.

Common Mistakes in Titration

The most common practical error is not standardizing the titrant against a primary standard before relying on its stated concentration, a titrant's actual concentration can drift from what the label says, especially for solutions like NaOH that absorb atmospheric CO2 over time. Dilutions Calculator's titration calculator guide also flags overshooting the endpoint, adding titrant too quickly near the color change, as a frequent source of error that inflates the calculated concentration. Adding titrant dropwise once the color starts to shift, and swirling continuously, are the two habits that fix most inconsistent titration results.