Modifiability of the Object-Oriented system with inheritance states that how much amount of information would be modified in the individual class level and total system level. Measuring the modifiability in the appropriate manner leads to improve the maintainability and also quality of the specified software system. Existed metrics for modifiability gives the more complexity values and typical to work with them. Here main concentration is on to consider the proper modifiability of the Object-Oriented system and reduce the complexity in judging the modifiability. The identified modifiability metrics of the class and system level are validated with the well known Weyker’s properties to strengthen the proposed metrics and which may utilized in their research work by researchers.