Measure the usable floor area
Measure the room after accounting for wardrobes, windows, switches and the preferred clearance on each side of the bed. The mattress size is only part of the final footprint; the frame adds its own width and depth.
King size gives more room, queen gives more flexibility
A king is useful when two sleepers want more personal space and the bedroom can support wider bedside clearance. A queen can preserve circulation in apartments and guest rooms.
Confirm mattress and frame compatibility
Ask for the exact mattress dimensions, platform height and delivery access before choosing a frame. This prevents a mismatch between a new bed and an existing mattress.