Eggs are graded to indicate interior and exterior quality (AA, A, B) and sorted according to weight (size). Grade quality and size are separate ratings and are not related. To pass grading, all eggs must be clean with sound shells.
Grade AA eggs must have an air cell less than 1/8” deep while Grade A eggs can have an air cell up to 3/16” deep. A freshly laid egg has a very small air cell that expands as the egg ages. After approximately 10 days, a Grade AA rated egg transitions to Grade A, as the air cell enlarges. There is no nutritional difference between Grade AA and Grade A eggs.
Egg size (small, medium, large, extra large, jumbo) indicates the minimum required weight per dozen, but does not reflect not the dimensions of the individual eggs. Large eggs, for example, have a minimum weight of 24 oz. per dozen; extra large eggs must weigh at least 27 oz. per dozen.
Remember, always purchase eggs before the "Sell-By" or expiration date printed on the carton. At home, refrigerated eggs will keep for 3 to 5 weeks from the date of purchase.