Stretch flange forming experiments of AA5182 and AA5754 sheet alloys were performed to characterize the forming properties. Identical blanks with the same cutout radius were deformed to 25, 50, 75, and 90% of the measured minimum punch depth to fracture. Strain development during stretch flange forming was tracked through strain measurement of the recovered deformation-interrupted samples. Finite element modeling of stretch flange forming was performed, and the resulted strain distribution along the stretch flange profile was compared to the experimental results. Good agreement was observed between the numerical and experimental results. Two failure modes observed in the stretch flange experiments, inner edge necking and circumferential cracking in sidewall, were related to the measured strain locus and sheet thickness.