1 credit hour is equal to how many hours?

Credit hours is a term that is basically used in the universities to allocate the hours given to a subject per week if there are 1 credit hour of a subject it's mean that the total number of classes in one week will be called you only one hour lecture so normally there are 2- 3 crediy hours allocated to a subject per week and it is multiplied with the the gained GPA of that subject to calculate the result.