Graphic illustration of a pie beside black Greek Pi symbol

Get Ready for Pi Day with These Weird and Wonderful Math Facts

Get Ready for Pi Day with These Weird and Wonderful Math Facts

On the 14th of March every year, we celebrate Pi Day. It’s a time to marvel at miraculous math (and maybe enjoy some tasty baked goods…) But what is “Pi”, other than a delicious treat?

Pie illustration with cherry cut-out on top Greek Pi symbol in black on white background

Pi, written with the Greek symbol π, is a special number that has fascinated mathematicians for millennia. Pi is the circumference of a circle divided by the diameter, a ratio of 3.14. We can’t say what pi is exactly, because its decimal places stretch on forever with no pattern. The closest we’ve gotten was last year, where computers calculated pi’s decimal places up to 13.3 trillion digits!

Today, scientists and engineers use pi for an amazing range of calculations involving circles and curves, from planning the routes of airliners to analyzing sound waves.

That’s a pretty weird and wonderful number. But what other incredible measurements are there? In honor of Pi Day, we’ve put together a list of the best and most bizarre units of measure from Johnny Ball's book Why Pi?. How many have you heard of?

1. Googol

In 1938, mathematician Edward Kasner invented the googol. His 8-year-old nephew came up with the name. It’s a REALLY, REALLY BIG NUMBER: 1 followed by 100 zeroes. The Google search engine was named after it.

2. Elephant

In the 19th century, they didn't have the paper sizes that we have today. Instead, paper came in sizes such as “foolscap” (16 1/2 x 13 1/4 in) to “elephant” (28 x 23 in). And if you really wanted to impress, you could write your essay on the largest size of paper available at the time: the double elephant.

Photo of elephant holding a stick in its swinging trunk

3. Sydharb

Some scientific Australians use this unit of volume to measure water. One sydharb is the amount of water in Sydney Harbour, which is about 900 billion pints.

4. Atomus

In medieval times, the Latin word atomus meant “a twinkling of the eye” – the smallest amount of time imaginable. Nowadays, it’s defined as precisely 1/376 of a minute, or about 160 milliseconds. See you in an atomus!

Graphic of blue eye with black pupil and white star

5. Beard-second

One beard-second is the length a man’s beard grows in one second: 5 nanometres (0.000005 mm). This not-entirely serious unit is used only by atomic physicists to describe the tiny distances that atoms and subatomic particles move in.

Sketch of James VI of Scotland leaning against table

6. Warhol

Andy Warhol once said that “in the future everyone will be famous for fifteen minutes.” So, a warhol is a measure of fame. 1 kilowarhol means being famous for 15,000 minutes, or approximately 10 days.

7. Apgar score

When you were born you were given an Apgar score. It’s the first test you took! The Apgar score evaluates the health of newborns immediately after birth, based on their Appearance, Pulse, Grimace, Activity, and Respiration. It ranges from 0 to 10.


Want to learn more about magnificent math and neat numbers? Johnny Ball’s book Why Pi? has got puzzles to solve, conundrums to crack and incredible tricks to show to friends. You’ll find out why maths isn't just numbers and sums, it's a fundamental, incredible, magical way to discover how everything works.

Buy the book

Buy the book

Why Pi? Why Pi?

This entertaining follow-up to DK's popular Go Figure!, Why Pi? presents even more mind-bending ways to Read more

This entertaining follow-up to Read more


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