The bed pillow sizes differ with the size of your bed. Also in different countries and continents there exist different pillow sizes.
In US there are in general three sizes of bed pillows. These are:
(1) Standard size is 20 x 26 inches
(2) Queen size is 20 x 30 inches
(3) King size is 20 x 36 inches
In other countries the size of bed pillows varies as
(1) Oxford size in German speaking countries is 20 x 30 inches
(2) Continental size in Continental Europe is 26 x 26 inches
(3) German bed pillow size is 40 cm x 80 cm
Above are general sizes but there is no hard and fast rule of bed pillow sizes as it can also be made on customer specifications. Size is depends upon bed size then also the way of sleeping.
Softness and hardness of bed pillow is defined by the type of filling. Different Filling can be done like Feathers,Downs & Polyester Fibres as per customer demand.