Why is a full turn 360 degrees, and not a nice round 100? The answer goes back about four thousand years, to ancient Babylon.
It started in Babylon
The Babylonians counted in sixties, not tens. That's why an hour still has 60 minutes.
Their astronomers watched the sun travel round the sky over a year: roughly 360 days, so about one step a day. They split that circle into 360 steps. That's most likely where degrees come from.
Why 360 stuck: it shares brilliantly
Cut a pizza fairly and every slice is a whole number of degrees:
- 2 people: 180° each. 3 people: 120°. 4 people: 90°.
- 5 people: 72°. 6 people: 60°. 8 people: 45°.
- 10 people: 36°. 12 people: 30°.
360 divides exactly by 24 different numbers.
Now try 100
Split 100 three ways and you get 33.333… forever. Not much use for cutting a pizza.
The French tried 400
After the French Revolution, France tried 400 to a full turn. Your calculator still has a GRAD button for it. Almost nobody uses it.
Share a pizza fairly between 9 people. What angle does each slice get?
Show the answer
360 ÷ 9 = 40°.
Save this for your next test
- A full turn is 360°.
- It most likely comes from Babylonian astronomy.
- 360 divides exactly by 24 numbers.
- Angle of each share = 360 ÷ number of shares.
Read the video transcript
- Why is a full turn 360 degrees? Why not a nice round 100?
- The answer goes back four thousand years, to ancient Babylon.
- The Babylonians counted in sixties, not tens. That's why an hour still has 60 minutes.
- Their astronomers watched the sun travel round the sky in a year, roughly 360 days, about one step a day.
- So they split that circle into 360 steps. That's most likely where degrees come from.
- But here's why 360 stuck: it shares brilliantly.
- Cut a pizza for 2 people: 180 degrees each. For 3: 120. 4: 90. 5: 72. 6: 60. 8: 45. 10: 36. 12: 30.
- Every one a whole number. 360 divides exactly by 24 different numbers.
- Now try 100. Split it 3 ways: 33.333, forever.
- After their revolution, the French tried 400 to a turn. Your calculator still has a GRAD button. Almost nobody uses it.
- Now you: share a pizza fairly between 9 people. What angle does each slice get? Tell me in the comments.
- Want maths to click like this? Book a free trial lesson at bloomeducationonline.com.
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