Buffers & pH calculators
The chemistry of acids, bases and buffers. Calculate the pH of strong and weak acids and bases exactly from their charge balance, use the Henderson-Hasselbalch equation, convert between pKa, Ka, pKb and Kb, plot a titration curve, and find a buffer's capacity and its response to added acid or base.
The recipe pages turn a target pH and concentration into masses to weigh for phosphate, citrate, acetate, Tris, TE and PBS. All are ideal-solution calculations at 25 °C and say so: the real pH depends on ionic strength and temperature (Tris especially), so a recipe is always confirmed with a calibrated pH meter.
pH Calculator (pH, pOH, Strong and Weak Acids)pH from [H⁺], pOH, strong acids and bases, or weak acids and basesOpen calculatorHenderson-Hasselbalch CalculatorBuffer pH, base-to-acid ratio, or pKaOpen calculatorpKa, Ka, pKb and Kb ConverterConvert between pKa, Ka, pKb and Kb of a conjugate pairOpen calculatorIonic Strength CalculatorIonic strength and Davies activity coefficients from the ions presentOpen calculatorOsmolarity CalculatorOsmolarity and osmotic pressure from solutes and dissociationOpen calculatorBuffer Capacity CalculatorBuffer capacity β, and the pH change after adding acid or baseOpen calculatorTitration Curve CalculatorpH against volume for a weak, strong or polyprotic acid titrated with baseOpen calculatorPhosphate Buffer Calculator (Sodium and Potassium)Masses of the mono- and dibasic salts for a phosphate buffer at a target pHOpen calculatorCitrate Buffer CalculatorCitric acid and trisodium citrate for a buffer at pH 3 to 6Open calculatorTris Buffer Calculator (Tris-HCl)Tris base and HCl for a target pH, with the temperature effectOpen calculatorPBS Recipe CalculatorSalt masses for 1×, 10× or 20× phosphate-buffered salineOpen calculatorTE Buffer Calculator (Tris-EDTA)Tris base, EDTA and HCl for TE at 1×, 10× or 100×Open calculatorAcetate Buffer CalculatorAcetic acid and sodium acetate for a buffer at pH 3.8 to 5.8Open calculator
Related equipment
Service documentation, failure modes and parts for the instruments these calculations are used with.