This titration calculator finds an unknown concentration from a titration: at the equivalence point, moles of titrant and analyte match by the reaction’s stoichiometry — so the unknown molarity falls straight out of the volumes.
Assumes the endpoint you read (indicator color change) matches the equivalence point. For diprotic analytes like H₂SO₄ against NaOH the titrant-per-analyte ratio is 2 (two protons to neutralize) — or 0.5 in the reverse direction.
The Equivalence-Point Equation
At equivalence, the titrant has delivered exactly enough moles to consume the analyte: M_titrant × V_titrant = ratio × M_analyte × V_analyte. Solve for the unknown and a buret reading becomes a concentration. This is analytical chemistry’s workhorse — vinegar acidity, water hardness, pharmaceutical assays and antacid strength all reduce to it. Solution preparation behind it uses our Molarity Calculator and Dilution Calculator. Part of our Chemistry Calculators collection.
Worked Example (Verified)
25.00 mL of unknown HCl, titrated with 0.100 M NaOH; endpoint at 22.50 mL:
- Moles NaOH delivered: 0.100 × 0.02250 = 0.00225 mol
- HCl + NaOH is 1:1, so moles HCl = 0.00225 mol in 25.00 mL
- Concentration: 0.00225 ÷ 0.02500 = 0.0900 M — three significant figures, because buret work earns them
- Flip it for H₂SO₄: the same data with ratio 2 gives 0.0450 M acid — the ratio field is where polyprotic honesty lives
Bench Details That Decide Accuracy
- Endpoint vs equivalence point: the indicator changes near, not at, equivalence — choose an indicator whose transition brackets the equivalence pH (phenolphthalein for weak acid/strong base, methyl orange for the reverse family).
- Rinse the buret with titrant, the flask with nothing but analyte (water in the flask is fine — moles, not concentration, is what the flask holds).
- The last drop matters: near the endpoint, add dropwise or half-drops; overshooting by 1 mL on 22.5 mL is a 4% error in one splash.
- Standardize the titrant first (NaOH absorbs CO₂ and drifts) — professional titrations calibrate the “known” before trusting it.
Related Tools
- pH Calculator — where the curve is heading
- Molarity Calculator — making the titrant
- Chemistry Calculators — the full collection
Frequently Asked Questions
How do you calculate concentration from a titration?
M_analyte = (M_titrant × V_titrant) ÷ (ratio × V_analyte). The example: (0.100 × 22.50) ÷ (1 × 25.00) = 0.0900 M. Volumes may stay in mL because they cancel.
What is the equivalence point?
The moment titrant moles exactly match analyte moles by the reaction ratio — the stoichiometric finish line. The endpoint is the observable signal (indicator change) chosen to land as close to it as possible.
What if the acid is diprotic?
Set the ratio to moles of titrant per mole of analyte: H₂SO₄ vs NaOH needs 2 NaOH per acid, so ratio = 2 when NaOH is the titrant. The calculator’s ratio field exists for exactly this.
Why is my calculated concentration always a bit off the class average?
Usually endpoint overshoot (the extra drop), reading the meniscus from above, or a titrant that wasn’t standardized. Systematic errors beat random ones in titrations — technique shows in the third significant figure.
Can this calculator do back-titrations?
Indirectly: run it twice — once for the total reagent added, once for the excess found by the back-titration — and subtract the moles (analyte = total − excess). The mole readouts here are sized for that bookkeeping.
Is this titration calculator free?
Yes — free, instant, no sign-up.