What’s the reason for eggs to be sold in dozen
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Also, they are sold in other amounts too. My supermarket has 6 and 24 count packages, at least.
12 is a very useful number. It can be divided by 2, 3, 4, and 6, whereas 10 for example can only be divided into 2 and 5. Being able to third and quarter something is very handy, which is why a lot of imperial measurements work that way – a foot is twelve inches instead of ten because a quarter foot and a third foot are whole numbers of inches. A mile is 5280 feet, which can be evenly divided by 2, 3, 4, 5, 6, 8, 10, 11, 12, and more. Volume measurements go in 2s, 3s, and 4s. 3 teaspoons to the tablespoon, 16 tablespoons to a cup, so a cup can be divided by 2, 3, 4, 6, 8, etc into an integer number of tablespoons and teaspoons. And so forth.
They aren’t everywhere. In Serbia they are sold in packs of 10, 20 or 30. People tend to stick to traditional measurements because that’s how systems (packaging, transportation, shelf space etc) get built and it’s a pain to change after. 12 has many divisors so it was a useful count to have of many things bought in bulk, so likely that just got solidified with eggs.
_Farmers and bakers adopted the practice of selling eggs and bakery items by the dozen as a way to make selling goods at market easier and to avoid making change. According to the New York Times, a farmer could sell one egg for a penny or 12 for a shilling (which equaled 12 pennies)._
Many things are packaged in 12s because it’s easy to break into different smaller sizes. You could buy 12 eggs, or your could buy 1/2 of that – 6, or 1/4 of that – 3. The seller just cuts the package and hands you the portion.
This is also why you’ll find the number 60 and 360 used. 60 is 3x4x5 and 360 is 3x4x5x6. Easy to divide into smaller portions, which is important not just for goods like eggs and buns, but also math when you have to divide before fractions were invented.
This is likely why we have 12 hours, 60 minutes, 60 seconds and 360 degrees in a circle.
Fun fact – the Babylonian number system was base 60, not base 10. They likely counted to 12 on their hand by tapping your thumb on each segment of your fingers – 3 segments on 4 fingers is 12. Count 5 fingers on your other hand for each 12 and you get 60. It’s the Babylonians who gave us our system of time.
12 is a vastly superior number to 10 as a basis. It evenly divides into halves, thirds, quarters, and sixths. It’s rare to need to split something five or seven ways.
They don’t. At least not everywhere. The most common egg carton in several European countries has 10 eggs. 6 or 4 are also available, but not 12.
Convention. What’s the easiest mental math that scales?
Egg used to be sold for one pence each in England back in the late 1500s. The shilling was equal to 12 pence and smart merchants began selling eggs in packs of 12 to get one whole shilling instead of a bunch of pence. This became known as English units and still exist today not only in the way eggs are packaged but also why beers are sold by the pint in bars, and wines are based on units of 750ml.
Anyway, English settlers brought their way of doing things to North America and the rest is history. You’ll notice other countries that don’t have a history with English units sell their eggs in different numbers and even by weight.
Additional information: There was a period of time where English speaking countries simultaneously used base-10 and base-12 counting systems. For 10 you use your fingers, for 12 you use your thumb to count the individual segments of the other fingers. We see vestiges of this in the language, too, like eleven and twelve not following the “-teen” convention
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