Buffer pH (Henderson-Hasselbalch)

Calculate the pH of a buffer from the pKa and the concentrations of the acid and its conjugate base, free online.

pKa of the weak acid

Acid [HA] (mol/L)

Conjugate base [A⁻] (mol/L)

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The Henderson-Hasselbalch equation is pH = pKa + log₁₀([A⁻] ÷ [HA]). A buffer works best within ±1 pH unit of the pKa; the buffer capacity is greatest when the acid and base concentrations are equal.