Average Bedroom Size typically range in size from 200-300 square feet, or roughly 12 x 15 feet or larger. This size provides enough space for a king-sized bed, several furniture items and even sitting areas. Master bedrooms often feature en-suite bathrooms and walk-in closets, further maximizing space. The design is geared towards comfort, privacy and opulence. Master bedrooms may differ in size depending on the layout of the house and budget, but they are typically the largest and most luxurious bedrooms in the house.