Henderson Hasselbalch Calculator
Calculate buffer pH from the ratio of conjugate base to acid.
About Henderson Hasselbalch Calculator
A buffer works best when the base-to-acid ratio is near one, which puts the pH at the pK_a. Beyond a tenfold ratio either way — one pH unit — buffering capacity falls off sharply. Choosing a buffer means choosing an acid whose pK_a is within one unit of the target pH; no concentration adjustment can compensate for the wrong pK_a.
Formula
Henderson Hasselbalch
pH = pK_a + log₁₀([A⁻] ÷ [HA])
- buffer range
- Roughly pK_a ± 1, where the buffer resists pH change effectively
Worked example
With the default values below, Henderson Hasselbalch Calculator returns Buffer pH of 4.7600. Change any input above and every figure here is recalculated in your browser.
Inputs used
- pKa of the acidaccepts -5–20
- 4.76
- Conjugate base concentrationminimum 0 mol/L
- 0.1 mol/L
- Acid concentrationminimum 0 mol/L
- 0.1 mol/L
- Buffer volumeminimum 0 L
- 1 L
Results
- Buffer pH
- 4.7600
- Ratio of Base to Acid
- 1.00000
- Total Buffer Concentration
- 0.20000 mol/L
- Lower End of the Useful Buffer Range
- 3.760
- Upper End of the Useful Buffer Range
- 5.760
Step by step
- 1Values used
- 2Henderson Hasselbalch
- 3Buffer pH= 4.7600
- 4Ratio of Base to Acid= 1.00000
- 5Total Buffer Concentration= 0.20000 mol/L
- 6Lower End of the Useful Buffer Range= 3.760
- 7Upper End of the Useful Buffer Range= 5.760
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 5 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 Henderson Hasselbalch calculated?
pH = pK_a + log₁₀([A⁻] ÷ [HA]) A buffer works best when the base-to-acid ratio is near one, which puts the pH at the pK_a. Beyond a tenfold ratio either way — one pH unit — buffering capacity falls off sharply.
Why does Henderson Hasselbalch matter?
Choosing a buffer means choosing an acid whose pK_a is within one unit of the target pH; no concentration adjustment can compensate for the wrong pK_a.
What values do I need to enter?
This calculator takes 4 inputs: pKa of the acid, Conjugate base concentration, Acid concentration, Buffer 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.