Titration Curve Calculator
Calculate pH at any point along a weak acid titration curve.
About Titration Curve Calculator
A weak acid titration curve has three regions: an initial pH set by the acid alone, a flat buffer region governed by the Henderson-Hasselbalch equation, and a steep rise past equivalence controlled by excess base. The flatness of the buffer region is precisely why buffers work, and its midpoint gives the pK_a directly.
Formula
Titration Curve
Buffer region: pH = pK_a + log([A⁻]/[HA]); past equivalence, pH follows excess hydroxide
- buffer region
- Between about 10 and 90% titrated, where pH changes slowly
- equivalence
- Where added base exactly matches the acid present
Worked example
With the default values below, Titration Curve Calculator returns pH at This Point of 4.5839. Change any input above and every figure here is recalculated in your browser.
Inputs used
- pKa of the acidaccepts -2–16
- 4.76
- Initial moles of acidminimum 0 mol
- 0.0025 mol
- Moles of base addedminimum 0 mol
- 0.001 mol
- Total volumeminimum 0 L
- 0.035 L
Results
- pH at This Point
- 4.5839
- Fraction Titrated
- 40.000%
- Acid Remaining
- 0.0015000 mol
- Conjugate Base Formed
- 0.0010000 mol
- Region of the Curve
- Buffer region — pH changes slowly
Step by step
- 1Values used
- 2Titration Curve
- 3pH at This Point= 4.5839
- 4Fraction Titrated= 40.000
- 5Acid Remaining= 0.0015000 mol
- 6Conjugate Base Formed= 0.0010000 mol
- 7Region of the Curve= Buffer region — pH changes slowly
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 7 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Titration Curve calculated?
Buffer region: pH = pK_a + log([A⁻]/[HA]); past equivalence, pH follows excess hydroxide A weak acid titration curve has three regions: an initial pH set by the acid alone, a flat buffer region governed by the Henderson-Hasselbalch equation, and a steep rise past equivalence controlled by excess base.
Why does Titration Curve matter?
The flatness of the buffer region is precisely why buffers work, and its midpoint gives the pK_a directly.
What values do I need to enter?
This calculator takes 4 inputs: pKa of the acid, Initial moles of acid, Moles of base added, Total volume. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.