How to Use the pKa & Ka Calculator
Convert acid dissociation parameters instantaneously:
Select Parameter
Choose input metric (pKa, Ka, or pKb).
Enter Value
Input numeric pKa or scientific notation Ka (e.g. 1.8e-5).
View Conjugate Pair
Get instant calculation of pKb and Kb for the conjugate base.
Evaluate Strength
Assess relative acid/base ionization strength and buffer ranges.
Key Features & Equilibrium Constants
Bidirectional Conversions
Convert freely between pKa, Ka, pKb, and Kb values.
Aqueous Kw Equilibrium
Uses Kw = 1.0 × 10⁻¹⁴ (pKw = 14.00 at 25°C).
Acid-Base Strength Classifier
Categorizes strong acids (pKa < 0), weak acids, and extremely weak acids.
General Chemistry Guide: pKa & Acid-Base Equilibria
The acid dissociation constant (Ka) measures the quantitative strength of an acid in aqueous solution:HA + H₂O ⇌ H₃O⁺ + A⁻ Ka = [H₃O⁺][A⁻] / [HA]
Because Ka values span many orders of magnitude, chemists express acid strength using logarithmic pKa:pKa = -log₁₀(Ka)A smaller or negative pKa value indicates a stronger acid that dissociates more completely in water.
Frequently Asked Questions
?What does a negative pKa mean?
A negative pKa (e.g. HCl pKa ~ -7, HNO₃ pKa ~ -1.4) indicates a strong acid that undergoes essentially 100% complete ionization in water.