High level synthesis tools transform an algorithmic description to a register transfer language (RTL) description of the hardware. The algorithm behavior is typically described in languages like C, C++ or their variants. The generated RTL is described in a hardware specification language like VHDL or Verilog. The size of the variables specified in the algorithm has a significant impact on the area of the generated hardware. The language accepted by the High Level Synthesis tools typically allow the size or bit width of a variable to be specified explicitly. This paper describes a method to automatically determine the minimum bit width of the variables from a performance profile. This would be effective to reduce the combinatorial and the non-combinatorial area of the generated hardware.