ChemBench

Henderson-Hasselbalch Calculator

The pH of any acid/base buffer.

pKa sets the baseline, the ratio adjusts it

When a buffer's conjugate base and weak acid are in equal concentration, pH exactly equals pKa — any imbalance in the ratio shifts pH up or down from that midpoint via the log term.

Why buffers resist pH change

This equation shows why buffers work: because pH depends on the log (not the raw ratio) of concentrations, even a several-fold change in the acid/base ratio only shifts pH by about 1 unit — this is what makes blood and lab buffers so stable.

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ChemBench

Henderson-Hasselbalch Calculator

The pH of any acid/base buffer.

pKa

[A⁻] conjugate base (mol/L)

[HA] weak acid (mol/L)

4.76

What you entered

pKa: 4.76[A⁻] conjugate base (mol/L): 0.1[HA] weak acid (mol/L): 0.1

1
Ratio [A⁻] ÷ [HA]
0.1 ÷ 0.1= 1
2
pH = pKa + log₁₀([A⁻]/[HA])
4.76 + log₁₀(1)= 4.76

Result

pH: 4.76

This buffer has a pH of 4.76.

pKa sets the baseline, the ratio adjusts it

When a buffer's conjugate base and weak acid are in equal concentration, pH exactly equals pKa — any imbalance in the ratio shifts pH up or down from that midpoint via the log term.