After the final expansion in Animal Crossing: New Horizons, your house can have six rooms.
The completed home consists of the original main room plus a back room, left room, right room, upstairs room, and basement. Tom Nook adds these spaces as you pay off successive home loans, gradually changing a small island house into a fully customizable residence.
The word “rooms” can cause confusion because players often count only the rooms branching from the main one. The main room is included in the total, making six rooms altogether. The upstairs and basement are also separate interior spaces, even though they are reached through stairs rather than ordinary doorways.
Home expansion is separate from island development. Building bridges, inclines, and public facilities does not increase the house’s room count. Once the final expansion is complete, players can still remodel the home, change its exterior, decorate every room, and expand storage, but there is no seventh standard room in the completed house.