Buffer Ratio & Stock Volume Calculator
Estimate conjugate-base and weak-acid amounts from a user-supplied pKa using the ideal Henderson–Hasselbalch relationship.
A QUICK WALKTHROUGH
How to use this tool
- [base]/[acid] = 10^(pH − pKa). Total formal buffer amount = target concentration × final volume. Acid and base amounts divide that total by the calculated ratio.
- Educational ideal-solution estimate only. You supply the pKa and two equal-concentration stocks. The calculation assumes activities equal concentrations, one weak-acid/conjugate-base pair, additive volumes, known stock concentrations, no salt hydration or purity correction, and no temperature or ionic-strength shift. It reports nominal stock and diluent volumes; it does not identify chemicals, give weighing instructions, certify compatibility or sterility, or produce a lab-grade preparation. Verify chemistry, safety data, actual final volume, and final pH with appropriate laboratory methods.
- Inputs and calculations stay in this browser.
Formula
[base]/[acid] = 10^(pH − pKa). Total formal buffer amount = target concentration × final volume. Acid and base amounts divide that total by the calculated ratio.
Assumptions and limits
Educational ideal-solution estimate only. You supply the pKa and two equal-concentration stocks. The calculation assumes activities equal concentrations, one weak-acid/conjugate-base pair, additive volumes, known stock concentrations, no salt hydration or purity correction, and no temperature or ionic-strength shift. It reports nominal stock and diluent volumes; it does not identify chemicals, give weighing instructions, certify compatibility or sterility, or produce a lab-grade preparation. Verify chemistry, safety data, actual final volume, and final pH with appropriate laboratory methods.
Local processing
Inputs and calculations stay in this browser.
GOOD TO KNOW
Common questions
Does this recipe guarantee a lab-ready buffer?
No. It is an ideal-solution estimate based on the pKa and equal-concentration stocks you enter. Verify the chemistry, safety, final volume, and pH with appropriate lab methods.
Why can the stock volumes exceed the final volume?
The selected stock concentrations may be too low for the target total concentration. Increase stock strength or reduce the target concentration.