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🧪 Buffer Preparation Calculator

Calculate exact volumes of acid and conjugate base to prepare any common buffer at your target pH, molarity, and final volume. Based on the Henderson–Hasselbalch equation.

Select Buffer System

📌 Phosphate buffer (pKa 7.2) — effective range: pH 5.8 – 8.0

Target pH

Total Molarity

Final Volume

Buffer Recipe

Component A

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Component B

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💡 Lab Tip: Always prepare buffer at room temperature, then adjust pH with a calibrated pH meter. Temperature shifts pKa slightly — for Tris buffer, pH drops ~0.03 units per °C increase. Verify final pH before use.

📦 Reagent forms: Molecular weights here assume the anhydrous form of each salt (or dihydrate for sodium citrate, the common reagent-grade form). If your reagent bottle says "hydrate," "dihydrate," or similar, check its actual MW on the label — using anhydrous MW for a hydrated salt will give you slightly less of the active compound than intended.

⚠️ Verify before use: This calculator is a convenience aid based on the Henderson–Hasselbalch equation. Always verify final pH with a calibrated meter before using the buffer in an experiment.

📖 Example (Phosphate Buffer pH 7.4): Select PBS, pH = 7.4, Volume = 100 mL → the calculator gives you exact masses of Na₂HPO₄ and NaH₂PO₄ to weigh. Verify with a calibrated pH meter after dissolving. Copy the result for your Methods section: "100 mL of 0.1 M sodium phosphate buffer, pH 7.4, was prepared using the Henderson–Hasselbalch equation."

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Henderson–Hasselbalch

All calculations use pH = pKa + log([A⁻]/[HA]) for accurate acid/base ratios.

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6 Buffer Systems

Covers the most common lab buffers: phosphate, acetate, citrate, Tris, HEPES, and carbonate.

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✔ Formulas last verified against primary references: March 2025 · Report an error

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Buffer preparation using the Henderson-Hasselbalch equation

Biological buffers maintain stable pH around an enzyme active site, in cell culture media, or during chromatography. The Henderson-Hasselbalch equation (pH = pKa + log([A−]/[HA])) describes the ratio of conjugate base to weak acid at a given pH. Choose a buffer whose pKa is within 1 pH unit of your target for maximum buffering capacity. Phosphate (pKa 7.2) is ideal for physiological pH 6.8–7.4. Tris (pKa 8.1) works at pH 7.5–9.0 but has a large temperature coefficient (ΔpKa ≈ −0.028/°C). Citrate (pKa values 3.1, 4.8, 6.4) suits lower pH ranges but chelates divalent metal ions. Always dissolve components in ~80% final volume, adjust pH with a calibrated meter, then make up to final volume. Report: buffer identity, concentration, pH, temperature of adjustment, and any additional salts.

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Scitero.com Buffer Preparation Calculator. Retrieved from https://scitero.com/tool-buffer-preparation.html