There are three main size classifications of donkeys: Mammoth, Standard and Miniature. Donkeys and other equines (mules, hinnies, horses and zebras) are measured at the highest point of their shoulders (the withers), and the result is referred to in terms of hands. Four inches equals one hand.
Standard donkeys range in size from 36 to 54 or 56 inches (depending on whether they are female or male). These donkeys come in a variety of colours and can be further classified into small standard (36-48 inches) and large standard (48-54 inches).

Joey, a lovely roan red standard donkey.