Buffer pH Calculator (Henderson-Hasselbalch)

Your details

Acid buffers use a weak acid and its conjugate base (e.g. acetic acid / acetate). Base buffers use a weak base and its conjugate acid (e.g. ammonia / ammonium).
In pH mode, enter your acid and base concentrations to compute the pH. In ratio mode, enter a target pH to find the [base]/[acid] ratio you need.
Choose a preset to auto-fill the pKa. Select "Custom" to enter your own value.
The negative logarithm of the acid dissociation constant Ka. If you have Ka, use pKa = -log10(Ka). For base buffers enter the pKa of the conjugate acid (= 14 - pKb at 25 degrees C).
Molar concentration of the weak acid component (or conjugate acid BH+ for base buffers).
mol/L
Molar concentration of the conjugate base component (or free base B for base buffers).
mol/L
Buffer pHGood buffer
7.2

pH calculated from the Henderson-Hasselbalch equation

[A-]/[HA] ratio1
Buffer capacity (beta)0.1152mol/L/pH
Effective range min6.2
Effective range max8.2
Required [base]/[acid] ratio1
Buffer effectivenessEffective (pH within pKa +/- 1 range)
7.2 pH
Strongly acidic<2Acidic2-5Slightly acidic5-7Slightly basic7-9Basic9-11Strongly basic11+

Buffer pH is 7.20.

  • The buffer pH is 7.20, which is slightly basic.
  • The acid and conjugate base are present in equal concentrations, so pH equals pKa - the maximum buffering condition.
  • Buffer capacity is 0.1152 mol/L/pH, which is strong. Higher total concentration increases capacity.

Next stepThis buffer is within the effective range (6.20-8.20). For best performance, keep the pH within 0.5 units of the pKa (7.20).

 = Powered by OnlyCalculators