Predicting of electro-mechanical behavior of ionic polymer metal composites (IPMCs) is important in many actuator design applications, but a general model for such predictions has not been successfully developed yet. A simple but versatile modeling method based on the concentrated ion boundary layer model was developed to advance the modeling of the bending behavior of IPMCs of different sizes. IPMC beams with different thicknesses and sizes were fabricated by stacking and hot-pressing method, and their mechanical bending characteristics were measured. Finite element analysis of the beams was performed using a concentrated ion boundary layer model that uses a thermal analogy. The calculated deformation and tip blocking force agreed well with the measured values for specimens of different sizes. This study shows that the proposed modeling method is simple but general enough to simulate the deformation characteristics of IPMC actuators of various sizes.