Single point incremental forming SPIF is a flexible manufacturing process that does not require a special die for each part and is conducted on CNC milling machine that control on the motion of the forming tool. The formability is very important in any forming process therefore this work is concentrated on the influence of some factors on formability during SPIF. The factors that were studied are: type of tool path, depth step, feed rate and tool rotational speed. Three factors (depth step, feed rate and tool rotational speed) are examined depending on three levels (low, medium and high levels) while the type of the tool path was examined depending on two levels (low and high levels). In this work the total number of experiments is 18 experiments except the screening experiments that were made beforethe main experimental tests. Response surface method is used to build the predictive model to predict the value of effective strain for experiments that are not experimentally conducted. The results show that the feed rate and interaction between step size and type of tool path have the largest effect on formability. It is found that the maximum value of formability in terms of effective strain was (ε ̅=0.5049) while the minimum value was (ε ̅=0.26456). It is also found that SPIF is affected by the friction at the interface between forming tool and sheet metal as in other metal forming processes.