Unified modelling language (UML) can be used to implement an object oriented software system, how to map this UML to function point analysis various approaches are suggested by software practitioners, we have used UML diagrams to map UML to function point analysis. Various rules were proposed earlier, these rules can be applied on UML to estimate function points. We have used UML class diagram for data function analysis and UML sequence diagram for transaction function analysis than we have applied transformation rules and guidelines to estimates function point. We have developed a tool based estimation technique for object oriented software metrics which extracts required information from UML diagrams and its logical view report to estimate size of software then using COCOMO II rest of the software metrics are calculated e.g. effort, development time, productivity and cost.