Ka, Kb, pKa and pKb Calculator
Moves between the four ways of stating the strength of an acid or base.
pKa
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pKb of the conjugate base —
Ka —
Kb of the conjugate base —
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The formula
pKa = −log₁₀ Ka pKb = −log₁₀ Kb Ka × Kb = 1.0 × 10⁻¹⁴ at 25 °C
The stronger an acid, the larger its Ka, the smaller its pKa, and the weaker its conjugate base.
What to watch out for
Each value describes a conjugate pair: entering the Kb of a base gives the Ka of its conjugate acid, not of some other acid.
Frequently Asked Questions
How do I convert pKa to Ka?
Raise 10 to the power of −pKa. A pKa of 4.76 is a Ka of 1.738 × 10⁻⁵.
What is the pKb of the conjugate base of an acid with pKa 4.76?
9.24, at 25 °C.