Henderson–Hasselbalch Calculator
⚖ Acids, Bases & Equilibrium. Use the Henderson–Hasselbalch (buffer) formula to find ph, pka, [a⁻], [ha]: pick the value you want, type the others, and the answer updates as you go.
pH4.76
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| pH | no unit |
| pKa | no unit |
| [A⁻] | mol/L |
| [HA] | mol/L |
Worked example
Find the ph when pKa = 4.76, [A⁻] = 0.1 mol/L, [HA] = 0.1 mol/L.
Using pH = pKa + log([A^-])/[HA]: pH = 4.76.
Frequently asked questions
What is the formula for Henderson–Hasselbalch (buffer)?
pH = pKa + log([A^-])/[HA].
What do the letters stand for, and what units are used?
pH, pKa, [A⁻] in mol/L, [HA] in mol/L.
How do you calculate ph?
Put the values into pH = pKa + log([A^-])/[HA]. For example, with pKa = 4.76, [A⁻] = 0.1 mol/L, [HA] = 0.1 mol/L, ph = 4.76.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (ph, pka, [a⁻], [ha]) and fill in the others: it rearranges the formula for you.
