Under a system that came to be known as English units, which was a combination of old Anglo-Saxon and Roman systems of measurement, eggs were sold by the dozen. It made sense to sell them that way because one egg could be sold for a penny or 12 for a shilling, which was equal to 12 pennies. That system held sway in the American colonies and persisted after the revolution, becoming part of the system known as U.S. customary units. Such units are used for consumer products and in industrial manufacturing.

The British have moved on, adopting a wholly new system of weights and measurements in 1824. But they still mostly sell eggs by the dozen.

Thus, in the United States, a vast majority of eggs are sold by the dozen, half-dozen and other multiples of 12. But in India and parts of Africa, it isn’t unusual to buy eggs by the piece, and in some countries they may be sold by 10s or 8s. Let’s just say it’s not an eggs-act science.

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