As a king’s dimensions are 76 inches wide (or 193.04cm) by 80 inches (or 203.2cm) long, and a single twin XL measures 38 inches wide (or 96.52cm) by 80 inches long (or 203.2cm), then it can be assumed that two twin XL mattresses put together—or two twin XL beds placed next to one other—can be the equivalent of a king-size bed.