In this paper, concise formulas for the intermodulation distortion of a bipolar common-emitter amplifier stage with arbitrary emitter impedance and input matching network are presented. These expressions provide quantitative insight in the influence of transistor properties, emitter degeneration and input power matching on distortion. Only a small set of measurable transistor parameters is needed. As examples, IIP3 is calculated for transistor only, transistor with emitter inductance, and transistor with emitter inductance and input matching circuit. Two transistors are compared: a double-poly Si transistor and a SiGe transistor in a similar process. A good agreement between analytical and numerical results is obtained.