Dozen.si
The AI guide to base-12 counting and the number 12 in everyday life
Why do we sell eggs by the dozen, split a foot into 12 inches, and put 12 hours on a clock face? Explore duodecimal (base-12) math and the surprising number of everyday units built on 12.
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What you get
Everything Dozen.si gives you
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Base-12 explained
Why 12's divisors made it a favorite counting base for centuries.
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Dozens in daily units
Eggs, inches, old British currency - where the dozen shows up in measurement.
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12 in time and sky
The 12-hour clock, 12 months, and the 12 zodiac signs, and where they came from.
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Go deeper
The number 12, explored
A tour of duodecimal math and the everyday units, currencies, and calendars built on the number 12.
Base-12 math
- Why 12 — 12 divides evenly by 1, 2, 3, 4, and 6 - more divisors than 10, which only has 1, 2, and 5.
- Duodecimal notation — A base-12 number system needs two extra digits beyond 0-9 to represent ten and eleven.
- Dozenal Society — Founded in the US in 1944 (and later in Britain) to advocate for base-12 counting reform.
Dozens in everyday units
- Baker's dozen — Thirteen for the price of twelve, often traced to 13th-century English bread-weight laws.
- 12 inches to a foot — The imperial foot has been divided into 12 inches since medieval England.
- Pre-decimal British currency — Before 1971, 12 pence made a shilling, and 20 shillings made a pound.
12 in time and calendar
- 12-hour clock — Ancient Egyptians divided daylight into 12 parts, a system that shaped the modern clock face.
- 12 months — The Roman calendar settled on 12 lunar-based months, later fixed to the solar year.
- 12 zodiac signs — Babylonian astronomers divided the sky into 12 constellations by around the 5th century BC.
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