Titration pH Calculator
Enter the acid and base concentrations and volumes to calculate the resulting pH - works for any point before, at, or after the equivalence point.
Last updated: September 26, 2026
Frequently asked questions
How do I calculate pH before the equivalence point?
Subtract moles of base from moles of acid to find excess H⁺, divide by total volume to get [H⁺], then pH = −log₁₀[H⁺]. This works because the strong base fully neutralizes an equal amount of acid, leaving the rest as excess.
What is the pH at the equivalence point for a strong acid/strong base titration?
Exactly 7 - at the equivalence point, moles of acid and base are equal, fully neutralizing each other and leaving only water and a neutral salt, with no excess H⁺ or OH⁻.
How do I calculate pH after the equivalence point?
Subtract moles of acid from moles of base to find excess OH⁻, divide by total volume to get [OH⁻], calculate pOH = −log₁₀[OH⁻], then pH = 14 − pOH.
Does this work for weak acids or weak bases?
No - this calculator assumes both the acid and base are strong (fully dissociate), which is what makes the simple excess-ion math valid. Weak acid/base titrations need equilibrium (Ka/Kb) calculations and produce a different, non-7 pH at the equivalence point due to the conjugate base or acid remaining in solution.
What happens to the pH exactly at the equivalence point if the volumes I enter are exactly matched in moles?
The calculator returns pH 7, since equal moles of a strong acid and strong base neutralize completely - if your acid and base volumes/concentrations give exactly equal moles, you've hit the equivalence point.
What's the pH after adding 40 mL of 0.1 mol/L base to 50 mL of 0.1 mol/L acid?
About 1.95 - moles of acid = 0.050 L × 0.1 = 0.005 mol, moles of base = 0.040 L × 0.1 = 0.004 mol, excess H⁺ = 0.001 mol over a total volume of 0.090 L, giving [H⁺] ≈ 0.0111 mol/L, so pH = −log₁₀(0.0111) ≈ 1.95.
Why does the total volume matter in the pH calculation, not just the leftover moles?
pH depends on concentration, not just the raw amount of excess ion - the same leftover 0.001 mol of H⁺ produces a different pH depending on whether it's diluted into 50 mL or 500 mL, so the calculator divides by the combined acid + base volume at each point.