The Twin XL and the California King are considerably different compared to above mentioned sizes; the California King dimensions are 72 inches wide (or 182.88cm) by 84 inches long ( or 213.36cm). On the other hand, the twin XL measures 38 inches wide (or 96.52cm) by 80 inches long (or 203.2cm). A quick comparison shows that a California King mattress is clearly 34 inches wider (or 86.36cm) and 4 inches longer (or 10.16cm) than a twin XL mattress.