Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

pH

Target pH of the buffer solution.

pKa

pKa of the buffering acid.

Apply the Henderson-Hasselbalch relation to compute the conjugate-base-to-acid ratio [A⁻]/[HA] = 10^(pH−pKa). The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

[A⁻]/[HA] ratio

Conjugate base to acid molar ratio.

• Concentration-based acid–base formulas usually approximate activities and may assume a fixed water ion product. Ionic strength, temperature, polyprotic equilibria, dilution volume, and activity coefficients can materially shift pH and speciation.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Henderson-Hasselbalch pH

  Estimate buffer pH from pKa and the ratio of conjugate base to acid concentrations.

• Buffer pH After Addition

  Compute the buffer pH after adding strong base as pKa plus log10 of conjugate base over remaining weak acid.

• Buffer Dilution pH Calculator

  Buffer pH remains unchanged upon dilution because Henderson-Hasselbalch ratio is preserved.