Approximate 'typical' max march size by keep level, assuming a normal (not maxed) progression of Rally Spot level, research, VIP, rank, and monarch gear for that keep level, plus optional March Size Increase item use (0/50/100/200%); NOT a true theoretical maximum since VIP/rank/monarch gear can exceed keep-level norms. Examples (no item used / with 200% item): k26 298,200 / 518,200; k28 492,200 / 782,200; k30 772,400 / 1,172,400; k32 971,400 / 1,471,400; k34 1,313,400 / 1,943,400; k36 1,769,500 / 2,539,500; k38 2,326,550 / 3,246,550; k40 3,427,500 / 4,527,500. At higher keep levels the breakdown increasingly includes General Equipment (Fearless Dragon/Ares Ring, Plantagenet Ring), March Size skillbook Lv4 (+12%), Dragon Celtic Demon (Lv6-10), Rally Spot Duty Officer (Special Officer +25%/+50,000, Toyotomi Hideyoshi +5%), Civilization Treasure Imperial Seal, and Ideal Land ornaments. Full derivation and all lever details are in 'How to increase March Size'.
Original research source: Evony Guide Wiki