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pKa Calculator

Convert between Ka and pKa for an acid.

 

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About this calculator

Use this calculator when a table mixes Ka and pKa and you need the one-line conversion before Henderson–Hasselbalch.

The calculation is pKa = −log₁₀ Ka, and Ka = 10^(−pKa). Type Ka as a number such as 1.8e-5, not as a pKa.

This is the definition only. It does not convert Kb or pKb, and it does not apply a temperature correction to Ka.

Convert: Ka to pKa, or the other way.

Ka or pKa: Ka (for example 1.8e-5 for acetic acid) or pKa (for example 4.76), matching the mode.

Result: pKa as a number, or Ka in scientific notation.