The equilibrium constant for the protonation of a base, B, 
: + H  
is an association constant, K, which is simply related to the dissociation constant of the conjugate acid, BH.
The value of  is ca. 14 at 25°C. This approximation can be used when the correct value is not known. Thus, the Henderson–Hasselbalch equation can be used, without modification, for bases.