Size service and feeder conductors from the demand load — with the overcurrent device, grounding electrode conductor, and equipment grounding conductor returned together, and the required ampacity shown so the selection can be checked, not just trusted.
For a 200 A dwelling service, copper, 30 °C ambient, three current-carrying conductors, the engine returns:
2/0 CU — OCPD 200 A · GEC 4 · EGC 6
Rendered from the same calculation library the form uses — computed at startup, never typed by hand, and golden-tested against the engine on every run.
A conductor is sized so it can carry the load continuously without exceeding its temperature rating, protected by an overcurrent device that matches. The calculation starts from the demand load, applies the adjustments the conditions require — ambient temperature, how many current-carrying conductors share the raceway — and returns the smallest conductor whose adjusted ampacity covers the requirement, along with the grounding conductors that pair with it. The intermediate values are shown because a sizing you can't check is a sizing you can't submit.
Method scope, stated honestly: 75 °C column only. Correct for the 100–400 A dwelling service/feeder range (110.14(C)(2)); optimistic for ≤100 A equipment, which 110.14(C)(1) puts on the 60 °C column.