Acid – base titration calculator
Balance acid and base equivalents, find an unknown concentration or required volume, and identify which reagent remains in excess.
Acid solution
Base solution
Live results
Acid and base equivalents are equal at the selected volumes.
Calculation breakdown
| Quantity | Acid side | Base side | Relationship |
|---|---|---|---|
| Concentration | 0.1000 mol/L | 0.1000 mol/L | Input |
| Volume | 25.00 mL | 25.00 mL | Input |
| Stoichiometric factor | 1 H⁺ | 1 OH⁻ | Input |
| Reactive equivalents | 2.500 mmol H⁺ | 2.500 mmol OH⁻ | Equal |
How to use this titration calculator
What this calculator does
This calculator applies acid – base stoichiometry to compare the amount of hydrogen-ion capacity supplied by an acid with the hydroxide-ion capacity supplied by a base. It calculates reactive equivalents, the base volume required for equivalence, and either solution concentration when the other concentration and both volumes are known. It also reports whether the current mixture is balanced, acid-rich, or base-rich. The calculation is a stoichiometric identity; it does not by itself predict the exact endpoint color, activity corrections, buffering behavior, or the pH of weak-acid and weak-base systems.
When to use it
Use it to plan a laboratory titration before filling the burette, check a recorded endpoint volume, determine an unknown analyte concentration from a standardized titrant, or compare polyprotic acids and multihydroxide bases by changing their stoichiometric factors. The underlying concept follows the IUPAC definition of titration: a measured reagent is added to determine the quantity of another substance through a known reaction.
How to calculate
- The calculator opens with a complete demonstration: 25.00 mL of 0.100 mol/L monoprotic acid and 25.00 mL of 0.100 mol/L monobasic base. The results and a validated example workbook are available immediately.
- Replace the acid values with your analyte or acid-side data, then enter the base concentration and delivered burette volume. Select the number of H⁺ or OH⁻ equivalents that participate in the neutralization.
- Read the neutralization balance and status first. Then use “Base volume at equivalence” for experiment planning or either derived concentration result for an unknown-solution calculation.
- Select “Download Excel” to export the current typed inputs and results. “Reset” clears the demonstration and all calculated content; export remains unavailable until a complete valid set is entered again.
Input guide
Acid concentration is a required positive decimal in mol/L, such as 0.100. Higher concentration increases acid equivalents and therefore increases the required base volume. Do not enter a percentage or mass concentration without first converting it to molarity. Acid volume is a required positive decimal in mL, such as 25.00; it is the measured analyte aliquot. A common mistake is mixing liters on one side with milliliters on the other. This interface expects milliliters for both volumes.
H⁺ donated per molecule is a required integer factor of 1, 2, or 3. Choose 1 for a one-proton neutralization such as HCl, 2 when two acidic protons are fully titrated, or 3 when three are fully involved. The factor is reaction-dependent: a polyprotic acid does not always release every proton under a particular endpoint condition.
Base concentration is a required positive molarity, for example 0.100 mol/L. Raising it lowers the base volume needed to neutralize a fixed acid sample. Base volume is the positive burette delivery in mL, such as 25.00. Read the delivered volume as final burette reading minus initial reading. OH⁻ donated per molecule is the base-side factor of 1, 2, or 3; calcium hydroxide commonly uses 2 when both hydroxides react.
Output guide
Neutralization balance expresses the smaller reactive-equivalent amount as a percentage of the larger, so 100% means stoichiometric equality and lower values mean one side is deficient. Acid equivalents and Base equivalents are millimoles of H⁺ and OH⁻ capacity calculated from concentration × volume × factor. Base volume at equivalence is the predicted mL of the entered base solution needed to match the acid equivalents exactly.
Acid concentration from base and Base concentration from acid rearrange the same equivalence equation. Use the derived value corresponding to the solution treated as unknown. Excess equivalents is the absolute difference between both sides, while Status identifies which reagent is in excess. These are stoichiometric results, not direct pH predictions. The breakdown table repeats concentration, volume, factor, and reactive equivalents so each result can be audited.
Worked example
For the startup values, acid equivalents are 0.100 mol/L × 25.00 mL × 1 = 2.500 mmol H⁺. Base equivalents are also 0.100 mol/L × 25.00 mL × 1 = 2.500 mmol OH⁻. Because the two amounts match, the neutralization balance is 100.00%, excess is 0.000 mmol, and the required base volume at equivalence is 25.00 mL. The same equation gives an acid concentration of 0.1000 mol/L from the base data. A strong-acid/strong-base system is often near pH 7 at equivalence, but weak systems may have a different equivalence-point pH; see this acid – base titration explanation for that distinction.
Formula and interpretation
n(H⁺) × Macid × Vacid = n(OH⁻) × Mbase × Vbase
At equivalence, reactive acid and base capacities match according to the balanced reaction. The molarity – volume products can be compared directly when both volumes use the same unit. This calculator reports millimoles because mol/L multiplied by mL gives mmol numerically. The IUPAC definition of a standard solution is useful when the titrant concentration is treated as known accurately.
Endpoint and equivalence point are related but not identical ideas. The equivalence point is the theoretical stoichiometric condition. The endpoint is an observed signal, such as an indicator color change or an instrument response. Good indicator selection minimizes the difference between them. For weak-acid or weak-base work, consult a full equilibrium treatment such as the pH calculations for acid – base titrations.
Common mistakes and practical limits
- Use the delivered burette volume, not the final burette reading by itself.
- Match stoichiometric factors to the balanced reaction and endpoint chemistry.
- Do not infer an exact pH from equivalents alone when weak species, buffers, or activity effects matter.
- Standardize titrants when high accuracy is required, and repeat trials until concordant readings are obtained.
- Keep all entered concentrations in mol/L and all volumes in mL; convert mass concentration before use.