pKa Calculator | PharmacyFreak

pKa Calculator

Find the pKa of acidic or basic drugs using % ionization and pH.
Educational tool for pharmacy students.

pKa Calculator Tool – Understand Drug Ionization Instantly

The pKa Calculator Tool is a student-friendly resource to help you understand how drugs behave in different pH environments. Designed for B. Pharm and medical students, this tool uses the Henderson-Hasselbalch equation to estimate the pKa of acidic or basic drugs based on the percentage of ionized form and environmental pH.

Whether you’re preparing for a lab report or mastering pharmacokinetics, this tool makes learning fast, visual, and interactive.

✅ Key Features

🧠 Educational Focus

  • Built for pharmacy and medical students

  • Helps explain the relationship between pKa, ionization, and drug absorption

🧮 Scientific Accuracy

  • Uses the Henderson-Hasselbalch equation

  • Supports acidic and basic drug types

🎯 Inputs

  • Drug Type: Acidic or Basic

  • pH of Environment: 0 to 14

  • % Ionized: 1% to 99%

📈 Outputs

  • Calculated pKa

  • % Unionized (auto-calculated)

  • Dominant Form (Ionized or Unionized)

  • Step-by-step formula explanation

  • Pie Chart of ionized vs unionized forms

User Guide: How to Use the pKa Calculator Tool

🔹 Step 1: Select Drug Type

Choose if the drug is Acidic or Basic.
This affects which form of the Henderson-Hasselbalch equation is used:

  • Acidic drugs:
    pKa = pH + log(% unionized / % ionized)

  • Basic drugs:
    pKa = pH - log(% unionized / % ionized)


🔹 Step 2: Enter pH

Input the environmental pH where the drug is dissolved.

Examples:

  • Stomach: ~1.5

  • Blood: ~7.4

  • Intestine: ~6.8 to 8.0


🔹 Step 3: Enter % Ionized

Provide the known percentage of drug in ionized form.
Example: If 80% is ionized, enter “80”.

The tool will automatically calculate:

  • % Unionized = 100 – % Ionized


🔹 Step 4: View Your Results

You’ll instantly see:

  • Calculated pKa value

  • % Unionized

  • Dominant form (ionized or unionized)

  • A pie chart representing both forms

  • A clear breakdown of the formula used

This gives you both numerical insight and visual clarity.


🔹 Step 5: Export or Reset

  • Click Export as PNG or PDF to save the chart and results

  • Click Reset to clear all inputs and try again

Quick Tip:

  • The closer the pKa is to the pH, the more balanced the drug is between ionized and unionized forms.

  • Unionized drugs absorb better (pass through membranes easily).

  • Ionized drugs dissolve better in aqueous environments.