In this paper, a geometrically scalable compact model for bipolar junction transistors, derived from the standard Mextram model, is proposed. According to the physical structure and critical dimensions of an NPN transistor, such as the length and width of its emitter, the initial model parameters are modified by introducing several dimension-related factors. The revised model is verified across various process technology nodes and platforms. The results demonstrate that our model has a remarkable scaling capability, and the RMS values are significantly lower than those of a MULT-scaling model. Therefore, our scalable compact model has a promising application in SPECTRE simulation of bipolar transistors in integrated circuits.