Why do pencils come in dozens of twelve?

Twelve divides by 2, 3, 4, and 6 with nothing left over. Twelve pencils can go six each to two people, four each to three people, or three each to four people with none left. Ten divides only by 2 and 5, so splitting it among three people leaves one pencil over. For the same kind of bundle, twelve is much easier to share than ten.

Back when people bought and sold goods at markets, they had to divide in their heads without a calculator. A bundle of twelve that could be split right away into halves, thirds, or quarters was convenient. Calling twelve dozens, or 144 items, a "gross" follows the same idea.

The English word dozen came through French from the Latin word for twelve, duodecim. In Japan it settled as "dāsu" (ダース), and it entered Korean as daseu (다스) unchanged. Korea's Standard Korean Language Dictionary lists daseu as a loanword for counting bundles of twelve and recommends using the Sino-Korean word "ta" (타, 打) instead.

A common misconception is that daseu means "one box" or "one pack." Daseu is a unit for counting, so twelve items make one daseu whatever the box looks like. Even if pencils are sold one by one, twelve of them together are still one daseu.

A year has twelve months, and a clock face shows the numbers 1 through 12. Because the clock face has twelve marks, the half, third, and quarter points land exactly on marks. The twelve animals of the East Asian zodiac also complete a full cycle in twelve. Some explain that bundles of twelve spread from counting the twelve finger segments of the other four fingers with the thumb, but this is not an established fact confirmed by records.

In Korea, eggs are mostly sold in tens or in trays of thirty, but in American supermarkets a carton of twelve is the standard. Next time you buy pencils or socks in bundles, think about how many people will share them. With a bundle of twelve, you can split it evenly among two, three, or four people.