Size                    Weight of a dozen eggs

Jumbo                              30 ounces
Extra Large                      27 ounces
Large                                24 ounces
Medium                            21 ounces
Small                                 18 ounces
Peewee                            15 ounces
Eggs sizes
U.S. sizes are defined by the weight of a dozen eggs. Not individual
eggs.  An egg in a carton of Extra Large eggs need not weigh at least
27/12 ounces, but the dozen must weigh at least 27 ounces.
The Fancy Chick
Rare and Heritage poultry