What percentage of the egg does the egg shell weigh?

The United States Department of Agriculture sizing is based by weight per ton. The most common U.S. size of chicken egg is 'Large' and is the egg size commonly referred to for recipes.

Chicken eggs are graded by size, for the purpose of sales. The egg shell constitutes 8–9% of the weight of the egg.

There are six sizes that egg come in they are as follows: Jumbo, very large or extra large, large, medium, small and peewee.

According to Tom Vasey, chair of the British Free Range Producers' Association, laying larger eggs is painful for the hen. "He recommends shoppers only to buy eggs of medium or smaller sizes". Professor Christine Nicol of the University of Bristol has stated 'There is no strong evidence of pain in egg-laying hens but it's not unreasonable to think there may be a mismatch in the size of birds and the eggs they produce. We do often spot bloodstains on the chicken egg.