A methodology to automatically convert fixed point data type representations into integer data types for high level synthesis is presented in this work. Our method converts all major C operations using fixed point data types into integer data types, models quantization and overflow modes, type conversion and casting. The conversion rule for each operation is described in detail as well as a regression test environment with 600 test cases to validate the method and to verify the correctness of each conversion compared to the same cases written in SystemC. The test environment converts each test case with fixed point data types into integer data types and synthesizes them with a high level synthesis tool to generate RTL. An RTL simulation is ran and the results in turn compared to the SystemC's OSCI simulation. For all of the 600 test cases the RTL simulation results matched the SystemC results proving that each conversion is accurately modeled. A larger real test case is also presented to validate the conversion method in a complex case.