Most children grow up sleeping in a twin or full-size bed, with a single pillow. But once you graduate to shopping for your own bedding, you are presented with a bewildering variety of pillow sizes and pillowcases to choose from. Pillowcase sizes can vary slightly between manufacturers, but generally measure the same as the pillow they're meant to fit, with about a half-inch of extra width and two or more inches of extra length so none of the pillow sticks out. Shams, another type of pillow covering, are usually the same width as pillow cases but a few inches shorter than a pillowcase.
Standard and Queen
Standard pillows are the size used most often on twin and full-size beds. A standard pillow usually measures 20 inches by 26 inches. The slightly longer queen pillow measures 20 inches by 30 inches. Standard pillow cases are designed to accommodate both standard and queen-size pillows, and typically measure 20 to 20.5 inches wide by 30 to 32 inches long. Queen pillow cases aren't very common, but when you find them they typically measure about 34 inches long. Standard pillow shams typically measure about 27 inches long, and queen-size shams usually measure about 31 inches long.
Extra-long king-size pillows, meant to span the entire width of a King-size mattress, measure 20 inches by 36 inches. The matching pillowcase usually measures 20 to 20.5 inches by 40 inches long. A king-size sham is typically about 37 inches long. In a pinch, you can also use two standard pillowcases to cover a single king-size pillow: slide one end of the pillow as far into the first pillowcase as it will go, then slide the other pillowcase over the bare end of the pillow so it overlaps the first pillowcase.
Travel pillows come in a wide variety of shapes, sizes and materials. Some are designed so you can launder the entire pillow, others come with their own removable cover. The typical travel-size pillow measures about 12 inches by 16 inches, so look for a pillowcase that measures about 12.5 inches by 18 to 20 inches. Note that this only works with rectangular pillows; doughnut-shaped travel neck pillows don't come with standard removable covers or pillowcases.
Decorative pillows come in almost as bewildering a variety as travel pillows, albeit larger. Some smaller decorative pillows, such as cylinder-shaped bolsters, don't have removable covers at all. The 26-inch-square Euro-style bed pillows can be covered with a Euro-style pillow case that typically measures 26-by-26 inches or slightly larger, or with decorative Euro shams. The remainder of decorative pillows are typically covered with shams instead of pillow cases; many shams come in the same standard, queen and king sizes as pillow cases.