How to use the buffer ph calculator
Find buffer pH from pKa and concentrations. Enter pka, conjugate base [a⁻], weak acid [ha] in the fields above; the buffer ph, ratio [a⁻]/[ha] are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- pKa — pKa
- A — Conjugate base [A⁻] (mol/L)
- HA — Weak acid [HA] (mol/L)
Worked example
With pka = 4.76, conjugate base [a⁻] = 0.2 mol/L, weak acid [ha] = 0.1 mol/L, the calculator gives buffer ph ≈ 5.06103; ratio [a⁻]/[ha] ≈ 2.
Frequently asked questions
What is the formula for the buffer ph calculation?
Buffer pH = pKa+log10(A / HA). Ratio [A⁻]/[HA] = A / HA. Here pKa is pka, A is conjugate base [a⁻] (mol/L), HA is weak acid [ha] (mol/L).
What inputs do I need for the buffer ph (henderson–hasselbalch) calculator?
You need pka, conjugate base [a⁻] in mol/L, weak acid [ha] in mol/L. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.