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NH₃ / NH₄⁺ Equilibrium Fraction Calculator

Fraction of un-ionized ammonia at a given pH.

Compute the fraction of total ammonia present as un-ionized NH₃ vs the ammonium ion NH₄⁺ at a given pH and temperature, using the NH₄⁺ pKa = 9.25 (at 25 °C). Useful for aquaculture toxicity assessment.

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

Inputs

mg/L

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

fraction NH₃ = 1 / (1 + 10^(pKa − pH))

In depth

Compute the fraction of total ammonia present as un-ionized NH₃ vs the ammonium ion NH₄⁺ at a given pH and temperature, using the NH₄⁺ pKa = 9.25 (at 25 °C). Useful for aquaculture toxicity assessment.