Electoral Boundaries Readjustment Act

Politicians Don't Draw Canada's Electoral Map. Here's Who Does — and How Your Riding Got Its Shape.

Canada's federal electoral map is redrawn after each decennial census in a two-stage process. First, a formula in the Constitution Act, 1867 allocates seats among the provinces: each province's population is divided by an electoral quotient, and two long-standing floors are then applied — the senatorial clause (no province gets fewer MPs than it has senators) and the grandfather clause (no province falls below a guaranteed historical seat count, updated in 2022 so that no province has fewer seats than it held in the 43rd Parliament). Second, the boundaries inside each province are redrawn by ten independent commissions, one per province, created under the Electoral Boundaries Readjustment Act. Each commission has three members: a chair, who is a judge appointed by the chief justice of the province, and two other members appointed by the Speaker of the House of Commons. Commissions publish proposed maps, hold public hearings, and consider objections filed by MPs through a House committee — but the commissions, not the politicians, have the final word. The system, in place since 1964, was built specifically to take boundary-drawing out of the hands of the governing party. The redistribution that followed the 2021 census added five seats — three in Alberta and one each in British Columbia and Ontario — bringing the House to 343 members, the map on which the 2025 general election was fought.