pKb Calculator Formula

Understand the math behind the pkb calculator. Each variable explained with a worked example.

Use the pKb Calculator

Formulas Used

pKb

pkb = -log10(kb)

Variables

VariableDescriptionDefault
kbKb (Base Dissociation Constant)0.000018

How It Works

How to Calculate pKb

Formula

pKb = −log₁₀(Kb)

Where:

  • pKb = negative base-10 logarithm of Kb
  • Kb = base dissociation constant

    • A lower pKb indicates a stronger base. pKa + pKb = 14 at 25°C for a conjugate pair.

    Worked Example

    Ammonia has Kb = 1.8 × 10⁻⁵.

    kb = 0.000018
    1. 01pKb = -log₁₀(Kb)
    2. 02pKb = -log₁₀(1.8 × 10⁻⁵)
    3. 03pKb = 4.74

    Ready to run the numbers?

    Open pKb Calculator