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# Buffer Calculator

A free online tool for buffer pH calculations. Approximate pH values are calculated with Henderson-Hasselbalch equation. It also provides a list of pKa values of buffers commonly used in biology and biochemistry.

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## Henderson-Hasselbalch Equation

Results obtained from Henderson-Hasselbalch equation are approximate and only valid for diluted solutions (< 100mM) and in the pH range of pKa ± 1. pH value is a reverse function of temperature (pH decreases with increasing temperature and vice versa). pH value may change after dilution of concentrated buffer stocks. pH value may be affected by salts and other solutes. It is recommended to check the actual pH value with a pH meter.

Fill all but one field and click 'Calculate':

 pH = pKa + log [A-] M mM [HA] M mM
 [A-] - concentration of the conjugate base [HA] - concentration of the conjugate acid

## pKa values of common buffers

 Buffer Useful pH Range pKa (at 25°C) Phosphate 1.7 - 2.9, 5.8 - 8.0 2.15, 7.20, 12.33 Glycine 2.2 - 3.6, 8.8 - 10.6 2.35, 9.78 Citrate 3.0 - 6.2 3.13, 4.76, 6.40 Acetate 3.7 - 5.6 4.76 MES 5.5 - 6.7 6.10 Bis-Tris 5.8 - 7.2 6.50 Carbonate 6.0 - 8.0, 9.5 - 11.1 6.35, 10.33 ADA 6.0 - 7.2 6.59 ACES 6.1 - 7.5 6.78 PIPES 6.1 - 7.5 6.76 MOPSO 6.2 - 7.6 6.90 Imidazole 6.2 - 7.8 6.95 Bis-Tris Propane 6.3 - 9.5 6.8, 9.0 BES 6.4 - 7.8 7.09 MOPS 6.5 - 7.9 7.20 TES 6.8 - 8.2 7.40 HEPES 6.8 - 8.2 7.48 DIPSO 7.0 - 8.2 7.60 MOBS 6.9 - 8.3 7.60 TAPSO 7.0 - 8.2 7.60 Tris 7.0 - 9.0 8.06 HEPPSO 7.1 - 8.5 7.80 POPSO 7.2 - 8.5 7.80 TEA 7.3 - 8.3 7.80 EPPS 7.3 - 8.7 8.00 Tricine 7.4 - 8.8 8.05 Gly-Gly 7.5 - 8.9 8.20 Bicine 7.6 - 9.0 8.26 HEPBS 7.6 - 9.0 8.30 TAPS 7.7 - 9.1 8.40 AMPD 7.8 - 9.7 8.80 TABS 8.2 - 9.6 8.90 AMPSO 8.3 - 9.7 9.00 Boric acid 8.5 - 10.2 9.23, 12.74, 13.80 CHES 8.6 - 10.0 9.49 CAPSO 8.9 - 10.3 9.60 AMP 9.0 - 10.5 9.70 CAPS 9.7 - 11.1 10.40 CABS 10.0 - 11.4 10.70