Correct me if I'm wrong, but IEEE 835 is a list of tables for several common configurations. For the nitty-gritty of calculating ampacity the IEEE Press Book "Rating of Electric Power Cables" takes it right from first principles. If you need a quick ampacity without pushing the installation limit IEEE 835 is the reference. My area (Ontario, Canada) electrical code has included some of the common configurations in the appendix, your's may as well.