Pillows are available in six sizes, which are directly proportional to the mattress size:
Standard size pillows measure 20 by 26 inches. This is the most common size and the number of pillows required is generally determined by the mattress size: one pillow for a twin sized bed, two for a double bed or queen sized bed and three for a king sized bed.
Queen size pillows measure 20 by 30 inches. This is an uncommon size pillow. In fact, queen size pillowcases don't really exist, so a standard size pillowcase is used. A queen size pillow fills a standard-sized pillowcase completely, resulting in a fuller feeling pillow (as it plumps up the pillow). The added length of queen size pillows allows it to fit perfectly on a queen size bed. Two queen-sized pillows are used on a queen size bed.
King size pillows measure 20 by 36 inches and are used on both standard king size beds and California king beds. Two pillows are used and the extended length means the pillows fit the mattress exactly. However, some people find these pillows to be too long and cumbersome, so in this case three standard sized pillows can be used on a king size bed.
Euro size pillows measure 26 by 26 inches. These large, square pillows are ideal for adding support and comfort or for propping you up to read. They also make great decorative bed pillows. Like the queen size pillow, there are no pillowcases specifically for euro size pillows.
Travel pillows measure 12 by 16 inches. These small pillows are great for car or plane rides or anywhere else you may require additional neck support and comfort. Travel pillows can be conveniently packed into suitcases. Body pillows measure as large as 75 by 15 inches. Body pillows are the largest type of pillow on the market. These pillows are designed to provide comfort and support to the entire body. They are designed to equal the average size of an adult and are often placed along the headboard of your bed or along a side of the bed, which faces the wall (if there is one). This type of pillow is also available in smaller sizes for children.