Calgary won the first-round series in seven games and will face the Medicine Hat Tigers next.
Chase Lang, Radel Fazleev and Kenton Helgesen also scored for the Hitmen, while Mack Shields made 11 saves for the win.
Captain Sam Reinhart and Jaedon Descheneau replied for Kootenay. Wyatt Hoflin stopped 29 shots in net for the Ice.
Rankin's second goal came on one of Calgary's three power plays. Kootenay did not score on its two man advantages.