Use this free online buffer calculator to choose a common buffer, set target pH and strength, select salt or hydrate forms, and scale a starting recipe by final volume. Search accepts common names, abbreviations, salt names, and formulas.
Useful Checks
Buffer Calculator separates pH-calculated buffers from fixed recipe templates so PBS, TAE, TBE, SSC, and TE are not forced into the wrong Henderson-Hasselbalch model.
Use the buffer search field for common names, abbreviations, salt names, and formulas such as KPi, KH2PO4, NaH2PO4, HEPES, TBS, or TAE.
Check the pH suitability status before weighing. A buffer can calculate mathematically but still be a poor choice for the requested pH.
Use the Molarity Calculator handoff when you want to edit imported components, change units, or build a larger multi-solute recipe around the buffer components.
Minimum Inputs Needed
Buffer name; the buffer list is searchable by full name, abbreviation, salt pair, formula, and common publication name.
Target pH from the buffer-specific pKa/useful-range slider.
Target concentration for calculated buffers, or recipe strength for template buffers, using the strength sliders or exact number fields.
Final volume in mL. Use the 0-1000 mL slider or type an exact value, including a value outside the slider range.
Dry component form or stock concentration when relevant.
What The Result Means
The suitability text tells you whether the target pH is inside the practical range stored for that buffer.
Near the edge of a range, verify the choice against the assay protocol and consider nearby buffers.
Outside the practical range, the calculator suggests alternatives where possible.
The recipe is a starting calculation, not a replacement for pH meter adjustment and protocol verification.
How To Use
Search for and select a buffer by common name, abbreviation, salt name, or formula.
Set target pH and buffer strength, or recipe strength for a fixed template.
Enter the final volume in mL.
For calculated buffers, choose Dry chemicals / concentrated liquid components or From component stock solutions.
Select the exact salt or hydrate forms. If a liquid acid panel appears, replace the default % w/w assay and density with the values from the bottle or SDS.
Click Calculate buffer recipe and review pH suitability, component amounts, warnings, and preparation notes.
Copy the recipe, or send its components to Molarity Calculator when you need editable units or additional solutes.
Calculated Buffers Versus Recipe Templates
Acid/base pairs: Sodium phosphate, potassium phosphate, acetate, carbonate-bicarbonate, and citrate use Henderson-Hasselbalch ratios where appropriate. Citrate uses and reports the nearest citric acid pKa.
Single buffer compounds: Tris, HEPES, MES, MOPS, PIPES, Bis-Tris, Bis-Tris propane, Good's buffers, imidazole, succinate, maleate, borate, and glycine are weighed or measured, dissolved below final volume, and then pH-adjusted.
McIlvaine buffer: This is a citrate-phosphate stock-mixing recipe using citric acid and disodium hydrogen phosphate stocks.
Fixed templates: PBS, TBS, TAE, TBE, SSC, and TE scale their stored component recipes by final volume and recipe strength. Changing target pH is a protocol decision rather than a Henderson-Hasselbalch recalculation.
Liquid acids: Recipes that use a liquid acid expose editable % w/w assay and density so the stock volume can match the reagent in the lab.
Example
For "50 mM potassium phosphate buffer, pH 7.4, 1 L", the calculator uses the phosphate pKa, splits the total phosphate between monobasic and dibasic potassium phosphate, reports the component masses for the chosen hydrate forms, and flags whether pH 7.4 is in range.
Wet-lab caution: Always confirm exact salt or hydrate form, supplier molecular weight, pH meter calibration, temperature, solubility, and biological compatibility. Dissolve components in less than the final volume, adjust pH, then bring to final volume.