Steel fiber reinforced concrete is used as a construction material in modern structures. Recent studies have shown that steel fiber can be used to improve the behavior of structures and increase the bending moment capacity and shear strength of reinforced concrete members.This research present and modify the nominal and ultimate bending moment equation, maximum and balance reinforcement indices and depth of compression zone for different types of reinforced concrete beams: single, double and T beams including the effect of steel fibers.The modified equations showed that the internal moment capacity of the beams with steel fiber increased by the amount ( ) which represent the participation of the steel fiber. The balance and maximum reinforced indexes ( & )decreased by ( ) for single, double & T-beam reinforced concrete, this means that the ductility increased by adding steel fiber. Also the depth of compression zone increased by a factor ( ) which is greater than (1.0). The modified equations are verified and applied on the reinforced concrete beams with steel fibers which tested in previous study, the theoretical results showed excellent agreement with the experimental values.