In 1957, Davies suggested a method based on calculating a value based on the chemical groups of the molecule. The advantage of this method is that it takes into account the effect of stronger and weaker hydrophilic groups.  The method works as follows:
where:
 - Number of hydrophilic groups in the molecule
 - Value of the  hydrophilic groups (see tables)
  - Number of lipophilic groups in the molecule