The standard size for a bed is typically determined by the country in which it is sold. In the United States, the most common sizes are twin, full, queen, and king. Twin beds are 38 inches wide by 75 inches long, full beds are 54 inches wide by 75 inches long, queen beds are 60 inches wide by 80 inches long, and king beds are 76 inches wide by 80 inches long. However, there are also variations in size within these categories, so it’s important to measure your space and consider your personal preferences when choosing the right bed for your home.