Why does an hour have 60 minutes?
Your clock still counts the way Sumerian scribes did more than 4,000 years ago. Ten fingers did not choose 60. Fractions probably did.
▶ Start the storyAn hour has 60 minutes because our clocks inherited a counting system from ancient Mesopotamia. , or base 60, originated with the Sumerians in the third millennium BC, passed to the Babylonians, and is still used, in modified form, for time, angles and geographic coordinates. We count 10 fingers and write numbers in tens, but time keeps a Sumerian habit.
Why 60? Nobody can prove one single reason, and the mathematician Otto Neugebauer warned that its origins are not as simple, consistent or singular in time as they are often portrayed. But one advantage is easy to see. The number 60 has twelve , so fractions come out clean. An hour splits evenly into halves, thirds, quarters, fifths, sixths, tenths and more: 30, 20, 15, 12, 10, 6, 5, 4, 3, 2 or 1 minutes. Sixty is also the smallest number divisible by every number from 1 to 6. Try dividing 100 into thirds and you see the problem.
12
That matters for ordinary life. gave merchants and buyers an easier time when they divided larger quantities of goods. In the late third millennium BC, a of about 30 kg was divided into 60 minas, and each mina into 60 shekels.
The idea then travelled. Ptolemy's Almagest, in the second century AD, used base 60 for fractions, and around the year 1000 the scholar Al-Biruni split the hour into minutes, seconds, thirds and fourths. European astronomers were still calculating in base 60 as late as 1671.
So when you say that a film is 1 hour 30 minutes, or that a circle has 360 degrees (six sixties), you are using a count that began on clay tablets between two rivers.
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Recap
We use 60 minutes and 360 degrees because Sumerians and Babylonians counted in sixties, a number with many neat divisions.
💡 A trick to remember it · Sixty splits like a pizza for any party of two to six: no crumbs left, which is why clocks never let it go.
Surprising fact · Cuneiform scribes had no zero at first, so 1 and 60 were written the same way.
Sources (1)
No source, no claim. Every fact in this lesson (16 claims) cites at least one of these.