Both king and queen mattresses are approximately 80 inches long. Some bedding stores offer an extra-long mattress, known as a "California" king, which is 84 inches long.
A king mattress is approximately 76 inches wide, while a queen mattress is approximately 60 inches wide.
The king mattress can accommodate two adult sleepers, with each sleeper having 38 inches of space. The queen mattress provides 30 inches of sleeping space per adult sleeper, which is actually 8 inches less than an adult sleeping alone on a twin bed would have.