Titration Calculator
Calculate titration parameters from acid and base concentrations, volumes, and ion donation values.
Supports molarity units from M to yM and 14 volume unit options.
Updated September 11, 2026
What is acid-base titration?
Acid-base titration is the standard laboratory technique for determining the concentration of an unknown acid or base. A solution of known concentration (the titrant) is added to a measured volume of the solution being tested (the analyte) until the reaction reaches its equivalence point — the moment when the moles of H⁺ exactly balance the moles of OH⁻.
This calculator automates the titration equation in all six directions. Enter any five of the six core parameters — acid concentration, acid volume, acid H⁺ donated, base concentration, base volume, and base OH⁻ donated — and the calculator instantly solves for the missing value. It also computes the pH of both the acid and base solutions, the resultant volume after mixing, and the pH of the combined solution.
Who uses this? Chemistry students working through titration problems, lab technicians preparing standard solutions, educators building problem sets, and anyone who needs to quickly cross-check acid-base calculations without juggling unit conversions by hand.
How to use this calculator
Set the reaction type
Use the "Is the solution neutralized?" selector to choose whether you are working with a known neutralization, an incomplete reaction, or an unknown state.
Select acid and base strength
Choose Strong, Weak, or Unknown for both acid and base. When you pick Weak, a Ka field appears automatically — enter the acid dissociation constant if you know it. Unknown treats the solution as strong for calculation purposes.
Enter values for at least five of the six core fields
Fill in concentration (in molarity), volume, and H⁺ or OH⁻ donated for both the acid and base sides. The calculator needs five known values to solve the sixth. The result appears instantly — highlighted in blue to show it was auto-computed.
Read the result and pH values
The auto-solved field shows your answer. The "Additional acid/base parameters" sections contain moles of H⁺, moles of acid, moles of OH⁻, moles of base, and the pH values — all updated in real time as you edit.
1Worked example — find the base concentration
You are titrating 50 mL of 0.1 M HCl (monoprotic, so H⁺ donated = 1) with NaOH (also monoprotic, OH⁻ donated = 1) and you used 50 mL of the base. What is the concentration of the NaOH solution?
Step 1 — Write the titration equation:
Step 2 — Substitute the known values:
Step 3 — Solve for the unknown:
Enter all five known values into the calculator and it will confirm the base concentration is 0.1 M — exactly what you would expect when equal volumes of equimolar strong acid and strong base are mixed.
2Diprotic acid — H₂SO₄ with KOH
Sulfuric acid donates 2 H⁺ per molecule, so H⁺ donated = 2. If you have 40 mL of 0.05 M H₂SO₄ and the KOH concentration is 0.2 M with OH⁻ donated = 1, the required base volume is:
Because sulfuric acid is diprotic, you need half the volume of base compared to the acid — a common mistake in lab preparations.
Formulas and variables
Core titration equation
At the equivalence point of an acid-base reaction, the total moles of H⁺ donated by the acid equal the total moles of OH⁻ donated by the base:
Moles and pH formulas
Moles of H⁺
Moles of OH⁻
Acid pH (strong acid approximation)
Base pOH and pH
Resultant pH after mixing
at equivalence (strong acid + strong base)
When there is excess acid, the pH is calculated from the leftover H⁺ concentration. When there is excess base, it uses the leftover OH⁻ concentration and converts through pOH.
Unit flexibility: The titration equation only requires that both volumes share the same unit — you can use mL on both sides, or L on both sides, or even mix mL and L as long as the ratio is consistent. Concentrations should also use the same unit for acid and base.
Tips and best practices
H⁺ and OH⁻ donated are always whole numbers
A monoprotic acid (like HCl) donates 1 H⁺. A diprotic acid (like H₂SO₄) donates 2. A triprotic acid (like H₃PO₄) donates 3. The same logic applies to bases — Ca(OH)₂ donates 2 OH⁻, NaOH donates 1.
Weak acid strength selection
When you select "Weak" for either the acid or base, a Ka field appears. This is the acid dissociation constant — a lower Ka means a weaker acid. You can still use the calculator without entering Ka if you only need the titration equation.
Beware of the unit dropdowns
Concentrations default to molar (M) and volumes to milliliters (mL), but the calculator supports units from yM (joktomolar) to M and from mm³ to US gallons. If you switch a unit after entering a value, the number stays the same but its meaning changes — always double-check after switching.
Use the Additional parameters sections
Expand "Additional acid parameters" or "Additional base parameters" to see moles of H⁺, moles of acid, moles of OH⁻, moles of base, Ka2, and the pH values — all auto-calculated as you work.
Pro Tip: If you know the pH of the acid solution and the number of H⁺ ions donated, you can enter those two values into the "Additional acid parameters" section — the calculator will back-calculate the acid concentration from the pH. The same works for base pH and OH⁻ donated.
Limitations
Simplified pH model. The pH and pOH formulas use the strong-acid approximation — they assume complete dissociation. For weak acids and bases, the actual pH depends on Ka/Kb and the equilibrium calculation is more complex. The calculator includes a Ka field for reference, but the pH result shown is based on the strong-acid model.
Resultant pH assumes strong acid + strong base. The pH of the mixed solution is calculated only when all reacting species are strong (fully dissociated). If you are mixing a weak acid with a strong base (or vice versa), the resultant pH will differ from the displayed value.
No activity corrections. The calculator uses molar concentrations, not activities. At high ionic strength (typically above 0.1 M), deviations from ideal behavior can cause noticeable errors in pH calculations.
Temperature dependence omitted. The pH scale and the Kw constant shift with temperature. This calculator uses the standard value of at 25°C. For work at non-standard temperatures, the pH results will be approximate.
Educational tool, not a substitute for lab analysis. This calculator is designed for learning and quick estimation. For precise analytical chemistry work, always verify results using calibrated instruments and follow your institution's standard operating procedures.
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