A split king mattress measures approximately 76 inches wide by 80 inches long, the same overall size as a standard king mattress, but it’s made up of two separate twin XL mattresses (each 38 inches wide by 80 inches long). This setup allows each side to be adjusted independently, which is ideal for couples with different sleep preferences or who use adjustable bed frames. The split design reduces motion transfer and allows for individualized comfort, whether that means different firmness levels or sleeping positions. It offers the spaciousness of a king bed while enhancing flexibility and personal support.