The measure of the disinfecting power of a substance that is determined by dividing the figure indicating the degree of dilution of the disinfectant that kills a microorganism within a given time by that indicating the degree of dilution of phenol killing the microorganism under similar conditions
Phenol is an aromatic organic compound consisting of a phenyl group attached to a hydroxyl group. It is also known as carbolic acid. It is the typical disinfectant used in determining the germicidal strength of another disinfectant.1
The phenol coefficient is a measure of the disinfecting power of a germicidal solution in relation to phenol. To calculate for phenol coefficient, the number indicating the degree of dilution of the disinfectant in which it kills the microorganism within a given time (i.e. in 10 minutes but not in 5 minutes) is divided by the number indicating the degree of dilution of phenol in which the latter kills the microorganism in the same period of time and under the same conditions. A phenol coefficient that is greater than 1 indicates that the disinfectant is more effective than phenol. In contrast, a phenol coefficient that is lower than 1 means the disinfectant is less effective than phenol.