A standard pillowcase is designed to fit both standard and queen size pillows. The dimensions of a standard pillowcase are typically 20 inches by 26 inches (51 cm by 56 cm) . The extra material on one end of the pillowcase can cover the longer length of a queen pillow and still look aesthetically pleasing. Some queen pillows can fit inside standard pillowcases depending on the brand, but a longer pillow might be a good idea for those who tend to toss and turn at night. King size pillowcases are meant to accommodate king size pillows and are typically the largest pillowcase sizes that most people go with. They measure 20 inches by 36 inches (51 cm by 92 cm) .