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Buffer Calculator

Estimate a buffer's effective pH range and buffer capacity from pKa and concentration.

Introduction

Buffer Calculator — Estimate a buffer's effective pH range and buffer capacity from pKa and concentration. Enter pKa, Total buffer conc. C (mol/L), [H⁺] (mol/L) to get an instant, accurate result.

Formula

Effective buffering range ≈ pKa ± 1 pH unit, the range over which a buffer can resist significant pH change.

Step-by-step

  1. Enter the pKa.
  2. Enter the Total buffer conc. C (mol/L).
  3. Enter the [H⁺] (mol/L).
  4. Click Calculate to see your result instantly.

Real-world example

Example: With pKa = 4.76, Total buffer conc. C (mol/L) = 0.2, [H⁺] (mol/L) = 0.0000174, the Buffer Calculator gives P Ka: 4.76, Effective Range Low: 3.76, Effective Range High: 5.76.

Frequently Asked Questions

Why is the range pKa ± 1?
Outside this range the ratio of conjugate base to acid becomes too skewed (beyond roughly 10:1 or 1:10) for the Henderson-Hasselbalch buffering action to remain effective.
How do I choose a buffer for a target pH?
Pick a weak acid whose pKa is as close as possible to your desired pH so the target falls within its pKa ± 1 range.
What inputs does the Buffer Calculator need?
You'll need to provide: pKa, Total buffer conc. C (mol/L), [H⁺] (mol/L). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Buffer Calculator?
The Buffer Calculator applies the formula exactly as calculated — Effective buffering range ≈ pKa ± 1 pH unit, the range over which a buffer can resist significant pH change. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Buffer Calculator free to use?
Yes, the Buffer Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Buffer Calculator

The Buffer Calculator uses a real, verifiable formula — Effective buffering range ≈ pKa ± 1 pH unit, the range over which a buffer can resist significant pH change. — so results are accurate every time, not an approximation.