Queen

Queen sits at 60 by 80 inches: 6 inches wider than a full and 5 inches longer, and the size the US mattress market organizes itself around. Where a listing shows a price, a photograph or a review without naming a size, queen is the safe assumption.

Two sleepers get 30 inches each, roughly the width of a crib mattress apiece. That is the practical minimum most couples accept for the long term. The 80-inch length clears anyone up to about 6 foot 2 without a foot over the edge, which covers most adults.

Everything around the mattress is the quiet advantage. Sheets, protectors, duvets, frames, headboards and platform bases are all stocked deepest in queen, so choice is broadest and prices are keenest. Moving it stays a two-person job, but 60 inches negotiates most stair landings that a 76-inch king will not.

The compromise shows up at 3 a.m. Thirty inches each is enough to sleep and not enough to be unaware of the other person. A restless partner, a wandering toddler or a dog all register. Rooms of about 10 by 12 feet and up hold a queen with clear floor on both sides. Anything smaller and the bed becomes the room.