About the Buffer Solution Calculator
What is the Buffer Solution Calculator?
A buffer resists pH changes because it contains a weak acid and its conjugate base. This buffer pH calculator applies the Henderson–Hasselbalch equation.
Choose a common buffer system or enter a pKa. It also gives the base-to-acid ratio needed to hit a target pH.
How to use the Buffer Solution Calculator
- Buffer System (sample: Acetic acid / acetate (pKa 4.76))
- Custom pKa (sample: 4.76)
- Conjugate Base Concentration [A⁻] (mol/L) (sample: 0.1)
- Weak Acid Concentration [HA] (mol/L) (sample: 0.1)
- Target pH (for the ratio needed) (sample: 5)
- Press Calculate Buffer pH (results also refresh as you type). The result card shows the Buffer pH, along with pKa used, Base : acid ratio, Ratio needed for the target pH and Effective buffering range.
Formula used
pH = pKa + log₁₀([A⁻] ÷ [HA])
- Ratio for a target pH = [A⁻] ÷ [HA] = 10^(pH − pKa)
Buffers work best within about ±1 pH unit of their pKa.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Buffer System | Acetic acid / acetate (pKa 4.76) |
| Custom pKa | 4.76 |
| Conjugate Base Concentration [A⁻] (mol/L) | 0.1 |
| Weak Acid Concentration [HA] (mol/L) | 0.1 |
| Target pH (for the ratio needed) | 5 |
| Result | Value |
|---|---|
| Buffer pH | 4.76 |
| pKa used | 4.76 |
| Base : acid ratio | 1 |
| Ratio needed for the target pH | 1.7378 |
| Effective buffering range | 3.76 – 5.76 |
Tips for using the Buffer Solution Calculator
- Blood is buffered by the bicarbonate system at about pH 7.4.
- Higher total concentration gives more buffer capacity at the same pH.