This calculator works out the unknown concentration of a solution from a titration, the classic laboratory method for finding how concentrated a solution is. In a titration, a solution of known concentration, the titrant, is added carefully to a measured volume of the unknown solution, the analyte, until the reaction between them is exactly complete, the equivalence point, usually marked by an indicator changing colour. At that point the moles of titrant added are related to the moles of analyte by the balanced equation, so knowing the titrant's concentration and the volumes lets you calculate the analyte's concentration. This is the everyday workhorse of analytical chemistry, used to find acid and base concentrations, to check purity, and to measure all sorts of substances. This tool does the calculation. You enter the concentration and volume of the titrant used, the volume of the analyte, and the mole ratio between them from the balanced equation, and the calculator returns the analyte's concentration, along with the moles of titrant and analyte and the ratio used. The results update as you type. Use it to find a concentration from titration results, to check laboratory work, or for chemistry study. The core relationship is that, at equivalence, the moles of titrant times the ratio give the moles of analyte, and dividing by the analyte volume gives its concentration. For a simple one-to-one reaction, such as a strong monoprotic acid with a strong base, the calculation reduces to the titrant concentration times its volume divided by the analyte volume. The mole ratio matters when the stoichiometry is not one-to-one, for instance a diprotic acid needing twice as much base, so set it from your balanced equation. Volumes can be in millilitres since they appear as a ratio.
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0.125 M
analyte concentration
Moles titrant0.0025 mol
Moles analyte0.0025 mol
Mole ratio1
At equivalence: moles analyte = moles titrant x (analyte:titrant ratio). Concentration = moles analyte / analyte volume. Set the ratio from the balanced equation.
How it works
The moles of titrant are its concentration times its volume in litres. At the equivalence point, the moles of analyte equal the moles of titrant multiplied by the analyte-to-titrant mole ratio from the balanced equation. Dividing the moles of analyte by the analyte volume in litres gives its concentration.
Worked example
Titrating 20 millilitres of an unknown acid with 25 millilitres of 0.1 molar base, in a 1 to 1 reaction, the moles of base are 0.1 times 0.025 litres, which is 0.0025 moles. At equivalence the acid is also 0.0025 moles, so its concentration is 0.0025 divided by 0.020 litres, which is 0.125 molar.
