Titration Calculator

How to Use This Calculator

1. Enter the molarity and volume of the acid, and the volume of base at the equivalence point.
2. Set the number of ionizable H⁺ per molecule for polyprotic acids (n_acid).
3. The calculator returns the base molarity. Extended tabs add weak acid pH and curve points.

Formula

Example

Frequently Asked Questions

• What is a titration? ▼
  Titration is a quantitative analytical technique where a solution of precisely known concentration (the titrant, in a burette) is slowly added to a solution of unknown concentration (the analyte) until the chemical reaction between them is complete. The completion point is called the equivalence point, detected by a color-changing indicator or a pH meter. From the volume of titrant used and its known concentration, the unknown concentration of the analyte is calculated. Titration is widely used in laboratories for quality control, pharmaceutical analysis, food chemistry, and water testing.
• What is the equivalence point? ▼
  The equivalence point is the exact moment in a titration when the moles of titrant added are stoichiometrically equivalent to the moles of analyte in the flask — that is, the reaction is theoretically complete. For a strong acid and strong base (monoprotic), pH = 7 at equivalence because the only species remaining is neutral water and the salt. For a weak acid titrated with a strong base, the conjugate base of the weak acid hydrolyzes in solution, raising the pH above 7 (typically 8–10). For a weak base titrated with a strong acid, pH < 7 at equivalence.
• How do I calculate molarity from titration? ▼
  The key equation is: M_acid × V_acid × n_acid = M_base × V_base × n_base, where M is molarity (mol/L), V is volume (in consistent units), and n is the number of ionizable protons (or hydroxide groups) per molecule. For example, 25 mL of HCl titrated with 20 mL of 0.1 mol/L NaOH: M_HCl × 0.025 × 1 = 0.1 × 0.020 × 1. M_HCl = 0.002 ÷ 0.025 = 0.08 mol/L. For sulfuric acid (n=2) titrated with NaOH (n=1), use n_acid = 2 in the equation.
• What indicator should I use? ▼
  Choose an indicator whose pH color-change transition interval brackets the equivalence point. For a strong acid + strong base titration (equivalence at pH 7), any indicator with a transition near pH 7 works: bromothymol blue (6.0–7.6), phenol red (6.8–8.4). For a weak acid + strong base titration (equivalence pH 8–10), use phenolphthalein (8.2–10.0 — colorless to pink). For a strong acid + weak base titration (equivalence pH 4–6), use methyl orange (3.1–4.4) or methyl red (4.4–6.2). Universal indicator changes through multiple colors and is only suitable for approximate measurements.
• What is pH at the equivalence point for a weak acid? ▼
  For a weak acid (HA) titrated to the equivalence point with a strong base like NaOH, only the conjugate base (A⁻) and water remain. The conjugate base partially hydrolyzes: A⁻ + H₂O ⇌ HA + OH⁻, raising the pH above 7. The approximate pH at equivalence is: pH ≈ 7 + 0.5pKa + 0.5log(C_eq), where pKa is the negative log of the acid dissociation constant and C_eq is the molar concentration of the salt at equivalence. For example, acetic acid (pKa = 4.75) titrated to 0.05 mol/L conjugate base: pH ≈ 7 + 0.5(4.75) + 0.5log(0.05) ≈ 8.72.

Related Calculators