Henderson-Hasselbalch Buffer pH & Conjugate Base/Acid Ratio Calculator

Evaluate pH = pKa + log₁₀([A⁻]/[HA]) and effective ±1 pH buffering range.

Buffer Solution pH
4.94 pH
Conjugate Base / Acid Ratio 1.5 : 1
Solution pOH (14 − pH) 9.06 pOH
Total Buffer Ionic Strength 0.25 M
Inputs
pK_a
Negative log of acid dissociation constant pK_a (4.76 for acetic acid).
M
Molar concentration of conjugate base [A⁻] in M.
M
Molar concentration of weak acid [HA] in M.
Results & Graph
Buffer Solution pH
4.94 pH
Conjugate Base / Acid Ratio
1.5 : 1
Solution pOH (14 − pH)
9.06 pOH
Total Buffer Ionic Strength
0.25 M

Buffer Solution pH

Graph 1 • Acid Pka Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 pH 4.0 pH 7.9 pH 50%: 2.56 pH 2.6 50% 75%: 3.75 pH 3.8 75% 100%: 4.94 pH 4.9 100% 125%: 6.13 pH 6.1 125% 150%: 7.32 pH 7.3 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Buffer Solution pH 4.94 pH Conjugate Base / Acid Ratio 1.5 : 1 Solution pOH (14 − pH) 9.06 pOH Total Buffer Ionic Strength 0.25 M
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Buffer Solution pH4.94 pHConjugate Base / Acid Ratio1.5 : 1Solution pOH (14 − pH)9.06 pOHTotal Buffer Ionic Strength0.25 M
Summary: At pK_a=4.76 with [A⁻]/[HA] = 1.5, buffer pH is 4.94 (pOH = 9.06, total buffer molarity 0.25 M).
Summary: At pK_a=4.76 with [A⁻]/[HA] = 1.5, buffer pH is 4.94 (pOH = 9.06, total buffer molarity 0.25 M).
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Formula & Mathematical Methodology: Henderson-Hasselbalch Buffer Reference Equation

pH = pKa + log₁₀(ConjugateBase A⁻WeakAcid HA)
pOH = 14 − pH
pH = pK_a + log₁₀([ConjugateBase A⁻] / [WeakAcid HA]); pOH = 14 − pH
  • acidPka: Acid Pka (pK_a)
  • conjugateBaseMolarity: Conjugate Base Molarity (M)
  • weakAcidMolarity: Weak Acid Molarity (M)

Rounding: Laboratory and clinical equations retain full floating-point precision and round displayed results to 2 decimal places.

Worked Example: Reference Calculation: Henderson-Hasselbalch Buffer

Evaluate pH = pKa + log₁₀([A⁻]/[HA]) and effective ±1 pH buffering range.

  1. Enter the reagent concentrations, assay readings, or clinical laboratory parameters.
  2. Compute the standard formula: pH = pK_a + log₁₀([ConjugateBase A⁻] / [WeakAcid HA]); pOH = 14 − pH.
  3. Review the primary result, supporting reference intervals, and 3 SVG visualizations.
Result: Evaluates Henderson-Hasselbalch Buffer via pH = pK_a + log₁₀([ConjugateBase A⁻] / [WeakAcid HA]); pOH = 14 − pH.

Frequently Asked Questions

What formula is used by the Henderson-Hasselbalch Buffer pH & Conjugate Base/Acid Ratio Calculator?

It computes pH = pK_a + log₁₀([ConjugateBase A⁻] / [WeakAcid HA]); pOH = 14 − pH and plots three custom SVG graphs showing parameter sensitivity and component breakdowns.

Can I compare different reagent dilutions or lab scenarios side by side?

Yes. Use the "Compare (0/3)" button to pin up to 3 scenarios side by side.

Are entered values stored on any server?

No. Every calculation runs 100% locally in your browser.

Science & Engineering · Analytical Chemistry & Lab Bench

Henderson-Hasselbalch Buffer pH & Conjugate Base/Acid Ratio Calculator: inputs, method, and how to read the result

Evaluate pH = pKa + log₁₀([A⁻]/[HA]) and effective ±1 pH buffering range.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Acid Pka: Negative log of acid dissociation constant pK_a (4.76 for acetic acid).
  • Conjugate Base Molarity: Molar concentration of conjugate base [A⁻] in M.
  • Weak Acid Molarity: Molar concentration of weak acid [HA] in M.

What the calculation includes

With the default values shown, Buffer Solution pH is 4.94 pH. The calculation follows Henderson-Hasselbalch Buffer Reference Equation; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Acid Pka from 4.76 pK_a to 5.24 pK_a changes Buffer Solution pH from 4.94 pH to 5.42 pH. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard IUPAC atomic weights, 25°C (298.15 K) reference thermodynamics, and published clinical literature equations.
  • Educational and laboratory reference tool only; clinical scoring calculators do not replace professional medical judgment or institutional protocols.

Scope: IUPAC / NIH Laboratory & Clinical Reference Standard Check the assumptions and limitations against your situation before relying on the estimate.

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