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Weak Acid pH from Ka Calculator

pH = −log√(Ka·C) — weak acid equilibrium pH.

Calculates the pH of a weak acid solution from its acid dissociation constant Ka and initial concentration using the equilibrium approximation.

Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

[H⁺] ≈ √(Ka × C); pH = −log[H⁺]

In depth

Calculates the pH of a weak acid solution from its acid dissociation constant Ka and initial concentration using the equilibrium approximation.