Henderson-Hasselbalch Calculator
Works out the pH of a buffer, or the mix that gives a target pH. Choose what to find; the unused fields are ignored.
Answer
—
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
pH —
Ratio of base to acid —
Reading this —
The formula
pH = pKa + log₁₀([A⁻] ÷ [HA])
When the acid and its conjugate base are equal, the log term is zero and pH equals pKa.
What to watch out for
Only the ratio matters to the pH. The total concentration decides how much acid or base the buffer can absorb, which the buffer capacity calculator covers.
Frequently Asked Questions
What is the pH of 0.2 mol/L ethanoate with 0.1 mol/L ethanoic acid?
About 5.06, taking the pKa as 4.76.
What ratio gives pH 5 with a pKa of 4.76?
1.74 parts base to 1 part acid.