Pillows are measured in inches, and sometimes in centimeters. If you’re not sure what size pillow you should get, measure your mattress’s width and work with what will fit best. For full, queen, king, and California king size beds, you may want at least two pillows to lay across the surface.
Just be sure to avoid pillow sizes that are too big. If the pillow is dangling off the edge of the bed, it may fall off while you sleep.