The difference of pillow size for twin, full, queen king size and cal king bedding
The pillow for twin size, full size and queen size bedding in most case are at same size. They are also known as standard pillow. They are 20x26”
The King size and Cal King size (California king size) pillows are same, they are 20x37”. But many king and cal king size bedding also use standard pillows.
The sizes are useful when you purchase your bedding set and sheets set. Many bedding in a bag bedding sets come with pillow shams, the sham size should match your pillows. For sheet set, if they include pillow cases the size also important. You should read the size chart carefully.
Sometimes the cushions are also called pillows. Example square pillows, breakfast pillows and so on.
By fill in, pillows can be divided into many kinds. The most popular pillows are filled in with man made fiber. Some pillows are filled with down or feature or down feature mix. Recently many new kinds of pillows are filled in with nature silk, cotton. In some Asian country even filled in with bamboo Charcoal, Silkworm feces
Notes: The pillows here are different from the body pillows. The body pillow can be used as part of bedding also for sofa, or even used inside a car.