A modern Haida would grow into a first-rate escort

How much larger would a rebuilt HMCS Haida need to be to remain comparably capable in a modern navy?

Roughly four to four-and-a-half times her original displacement, because the modern equivalent of her role is a much larger first-rate escort.

A ship with Haida's relative competence in a modern fleet would need roughly four to four-and-a-half times her displacement. Second World War destroyers were second-tier general-purpose ships, whereas modern destroyers occupy the first-rate escort role once associated with cruisers. A literal small-hull recreation would miss the historical relationship between size, mission, and fleet hierarchy. The comparison shows how warship categories expand over time.